With the Earth getting hotter, time is running out for coal and other fossil fuels. We will be using more and more renewables like the Sun and the wind to power our homes, offices, factories and vehicles. But these sources of energy are not consistent. There are cloudy days and still nights. So, renewables work best with some kind of energy storage. Usually a battery that stores surplus energy when it is available, and supplies it when the Sun isn’t shining, or the wind isn’t blowing.
Sodium’s Moment
One interesting thing about Volta’s battery was that it used either ordinary salt water or caustic soda as an electrolyte between plates of different metals. Both salt and ‘caustic’ are compounds of the metal called sodium. Lithium, the wunderkind of modern batteries, wasn’t discovered until 17 years later.
After debuting on the battery stage, sodium left the scene like a one-song wonder. But it seems to be on a comeback tour now. Last year ended with Mukesh Ambani’s Reliance Industries picking up a $135-million stake in the British firm Faradion that has a head start in the field of sodium-ion batteries.
Other firms like California-based Natron (the name’s derived from sodium’s Latin name natrium) and China’s CATL have also rapidly improved their sodium-ion technologies. And there are many others.
So, why this sudden interest in sodium batteries? Are they better than lithium batteries? Will they allow cars to go 1000km on a single charge? Will they give your phone a week’s battery life?
Poor Man’s Lithium
Not really. Sodium and lithium are cousins on the periodic table. They live in the leftmost block. Lithium is one floor above sodium, and they behave alike in many ways, but lithium always tops the battery class. So sodium is the poor man’s lithium, and that’s what has made it so attractive now.
The problem with lithium is that its demand and price have hit the stratosphere. Lithium is a relatively scarce metal but everything from shavers to laptops and electric cars uses a lithium battery these days. So, the price of lithium hydroxide, which is a key raw material for making lithium-ion batteries, has shot up from about $4,500 in 2012 to almost $80,000. That’s why Elon Musk, the world’s richest man who needs tonnes of lithium to make Tesla cars and giant storage batteries, tweeted in April: “Price of lithium has gone to insane levels!”
But sodium hydroxide was at just $800 per tonne at the time. That’s to be expected because there’s hundreds of times more sodium than lithium in Earth’s crust, and it’s everywhere. With its vast coastline, India has an inexhaustible supply.
Not The First Choice
It’s abundant but sodium has some downsides as a battery material. Ounce for ounce, sodium batteries store less charge than lithium batteries. So you need a heavier battery for the same capacity. That’s why when the uses for rechargeable batteries were limited – camcorders and feature phones – scientists focused on developing lithium battery technology. In fact the 2019 Nobel in chemistry went to scientists who had worked in this field.
Sony launched the first gadget with a rechargeable lithium battery – a handheld video camera – in 1991. Since then, lithium batteries have improved a lot. The latest ones can be charged and discharged thousands of times. Current sodium batteries have a lot of catching up to do in this respect.
There’s also the question of scale. Although lithium is expensive, the scale at which lithium batteries are made keeps them affordable. Sodium batteries are expected to be 40% cheaper eventually, but that won’t happen until manufacturing scales up.
Made For Heavy Lifting
But sodium ion batteries have many advantages besides the promise of lower prices. Sodium itself is easy to extract and its batteries do not require cobalt – a metal mined at great human cost in central Africa.
While sodium batteries don’t store as much energy as the latest lithium batteries, by weight, they are far better than lead acid batteries used to start cars, and have reached the level where lithium batteries were a few years ago.
Faradion claims its batteries store about 160 watt-hours of energy per kilogram, which is similar to lithium batteries based on the older ‘lithium iron phosphate’ (LFP) technology. And with money pouring in for research, sodium batteries will keep getting better, even if they never catch up with lithium batteries.
Unlike lithium batteries, sodium batteries can be discharged completely for transportation, which eliminates the risk of fire in transit. They lose very little charge in cold conditions, and best of all, as they are very similar to lithium batteries, they can be made in the same factories without major retooling.
So, coming back to the question – is sodium about to dethrone lithium in the battery universe? The answer is they both might be kings in a battery multiverse. Lithium will remain the first choice for powerful cars, laptops and phones, while sodium will be a better fit for applications where high battery weight or low energy density do not matter. Giant storage batteries that power the grid, home inverters, and short-range vehicles like e-rickshaws and city cabs could all be run on it.
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