Raphael Thys
Salt crystals — Pexels
As the world turns its back on planet-wrecking fossil fuels, it starts to revolve more around batteries. EVs, solar power, wind power, tidal power, wave power, and even local energy grids will rely on them to function. But our current battery technology is bulky, expensive, and harmful to the environment, and as such, we desperately need a battery revolution. Luckily, a recent paper detailed a battery that solves pretty much all these issues. But will it be enough?
This battery is a sodium-sulphur molten salt battery. It uses liquid molten salt as its electrolyte and has existed for a long time now (read more about molten salt batteries here). These batteries tend to be cheaper, safer, and more environmentally friendly as they use a smaller amount of widely available materials (in that they don’t require ecosystem-damaging mining practises to source them like lithium-ion does), are non-toxic, and are non-flammable.
Previous molten salt batteries use aluminium-sulphur chemistries, and they tend to have a low energy density and require high temperatures to keep the salt molten, making them relatively useless. But this new one instead uses a unique sodium-sulphur chemistry and a salt that melts at room temperature, making it far more usable, cheap, and eco-friendly than other molten salt batteries. To test this, researchers created a button-cell prototype and put it through its paces, and what they found was remarkable.
Firstly, this battery was incredibly energy dense at 1,017 mAh/g. For some comparison, high energy density lithium-ion batteries are around 250 mAh/g, meaning this battery is four times as energy dense!
Now, there is no data on how much a battery like this would cost. However, estimates for a different molten-salt battery that uses more expensive materials are about $15 per kWh. For comparison, current lithium-ion batteries cost around $132 per kWh. So, assuming this new molten salt battery is of a similar cost, it would be about 90% cheaper than current cells.
Because this new molten salt battery operates at room temperature, it could, in theory, be used in an EV. All you’d need is a small secondary battery to power a heater in cold weather.
So is this the ultimate EV battery? If you used these in a car like the Tesla Model S, you could install four times the capacity with no weight gain, giving a range of 1,620 miles. Moreover, this mega battery pack would cost less than half of the pack Tesla currently uses! In other words, using this battery would make EVs nearly perfect.
Or would it?
You see, the tests of this battery showed that after 1,000 charge cycles, its capacity dropped by 50%. While this means that our hypothetical Model S would experience this drop after 1.6 million miles, for more affordable vehicles that use more miniature packs, this level of degradation would give them too short a life cycle to be viable. Now, because this was a test cell, it wasn’t designed to have a long life, so this is actually surprisingly good. This also means that future versions of this cell could be refined and developed to last much longer.
But as it stands, this awesomely cheap and eco-friendly cell is more suited to being used as a renewable energy grid-storage battery. Its safe nature and super low price more than make up for its short lifespan. Plus, because this battery is built of incredibly accessible materials, it can be used to rapidly expand our grid-storage capacity without being held back by supply chain issues or causing the price of EV batteries to skyrocket as demand outstrips supply.
This is why the researchers are now developing a larger pouch cell (like those that power your phone and laptop) version that could be used in just this way. So, that battery revolution we so desperately need could be about to happen. Let’s just hope it isn’t too late.