Salt-powered cars could save the world

Salt could save the world. A new battery technology is emerging, and it’s cheap. It could be the material that finally makes big batteries inexpensive and powerful.

You find sodium sitting right under lithium in the periodic table because they share similar chemical properties.

The way lithium ions function is essentially the same way sodium ions do. Sodium plays the same role in the battery, with the major downside being that sodium atoms are bigger and heavier.

“Manufacturing-wise, it’s a drop-in technology,” Deakin University’s Alfred Deakin Professor Maria Forsyth told Cosmos magazine in a recent interview.

Using sodium instead of lithium makes a battery less efficient per unit of weight, but much cheaper. Sodium can also make other parts of the battery easier to work with, including anodes and current collectors, making batteries even cheaper.

All these reasons are why a sodium-battery car has been unveiled in China in 2023 (made by JAC Motors, which doesn’t sell into Australia). Major Chinese manufacturer Chery (which does sell into Australia) has leapt on board too, pledging to use a sodium ion battery from mega-battery maker CATL in a new car soon.

While Western manufacturers may make tiny volumes of electric vehicles (EVs) for branding and regulatory reasons, China is pumping out millions. Its cost-conscious consumers have driven down the price and are a big reason for the rising EV penetration in Australia. BYD and MG are both Chinese brands — even the Teslas that Australia gets are all made in China.

The lithium problem

Lithium is tricky. It’s rare. Not as rare as gold, but rare. And it’s not available to every country. We have a lot, but China, not much. That is highly motivating when trade wars loom. Sodium, meanwhile, is everywhere and available to everyone.

Lithium is lightly concentrated in the earth’s crust. To mine a kilogram, you need to dig up an awful lot of ore. The world has 22 million tonnes of lithium which is sufficiently concentrated and close enough to the surface to be viable to dig up.

Let’s do the maths. There are eight kilograms of lithium in a small EV battery. So those 22 million tonnes could make almost 3 billion car batteries. However, there are 63 kilograms of lithium in a Tesla Model S battery, meaning that lithium would make only 350 million such batteries. That’s not enough.

Australia buys a million new cars a year. The world buys 60-75 million new cars each year, and rising. If all cars had Model S batteries we’d have enough lithium for six years. If all cars had small batteries, we’d have enough lithium for 60 years. Either way you can see a case for an alternative to lithium batteries.

The price is high

Lithium’s price has oscillated wildly recently, before settling at 200,000 yuan a tonne of carbonate (a salt form of lithium that is stable). At current exchange rates that is A$41,000 a tonne, or $41 a kilogram of lithium carbonate. Lithium carbonate is about one-fifth of lithium, by weight, so the price of pure lithium is about $200 a kilo.

But recently lithium carbonate prices have been as much as three times higher, as this chart shows.

You can see why a year ago it became vital to expedite lithium alternatives. The falling price of lithium since then is partly due to extra work by lithium miners to find reserves and exploit them. But to some extent it may also be an acknowledgment that alternatives have progressed.

We need more EVs

Australia is late to electric vehicle adoption. Only a few percent of new vehicle sales are EVs. We’ll have internal combustion engines on the road for a very long time. The reason people aren’t buying EVs is they are expensive. The cheapest new EV is about $40,000 compared with about $20,000 for the cheapest new petrol car.

Manufacturers need to figure out a way to make EVs cheaper if they are going to capture the bottom end of the market and chase cheap fossil-fuel vehicles off the road. That’s where sodium-ion batteries come in. They are heavier and less powerful per kilogram than lithium-ion batteries. But they can still play a role in many vehicles where power and speed aren’t so vital.

Lithium is not the only thing in a battery, but using sodium is expected to make batteries 30-40% cheaper. It’s easy to imagine a future with two tiers of EVs. Jaguars and Teslas will have lithium batteries and go like a rocket, eating up hundreds of kilometres before needing a charge. Meanwhile most people drive cheap Chinese EVs with smaller, cheaper, less powerful sodium batteries, an upside of which is they won’t blow up like lithium ones.

Sodium batteries can also do a lot of good work in stationary energy. It’s likely there’ll come a point where using lithium in batteries that don’t move around seems wasteful. Turning our renewables into reliable power depends on dispatchable, cheap storage. Sodium batteries could easily fill that role.

Sodium batteries are a much more realistic prospect than the recently floated plan to turn every farmer’s dam into a little hydro station. The sad reality of using gravity to store electricity is it’s simply not very efficient. You need large vertical distances, and preferably a substance much heavier than water to make it generate significant electricity at small scale.

The future is not in fresh water. It’s in the brine.

There’s still a $20,000 price premium for EVs, and that will last for some time if we’re stuck on lithium. Sodium offers the possibility of a two-tier battery situation in EVs — cheap, heavy EVs with sodium batteries and expensive lithium batteries for the most expensive cars. That’s not so different from the range of power options and fuel types in combustion engine cars, and is likely the answer to fully electrifying our fleet.