CATL's second-gen sodium-ion battery

Photo by: InsideEVs

From Inside EVs

China is reaching new heights in diversifying the battery chemistries used in electric vehicles. The country is already leading in subcategories of lithium-based chemistries, like nickel-manganese-cobalt (NMC), nickel-aluminum-cobalt (NCA) and lithium-iron-phosphate (LFP). Earlier this year, state-run utility company China Southern Power Grid even deployed sodium-ion batteries for stationary energy storage. Now CATL, the world's largest battery maker, claims to have unlocked new levels of extreme weather performance with sodium-ion batteries.

The role of sodium ions is similar to lithium ions, where charge-carrying ions travel between the positive and negative electrodes during the charge and discharge cycles. Studies suggest that sodium-ion batteries could eliminate the pesky traits of lithium-ions: There’s less risk of thermal runaway, they can operate at varied temperatures and crucially, the cost of sodium hydroxide, a key raw material, is far lower than lithium-hydroxide. (Although battery companies have reached better economies of scale with lithium-ions.)

Sodium-ion batteries have already entered production in China. Cars that use them include the Yiwei EV produced by Volkswagen-backed JAC and the JMEV EV3. Speaking at the World Young Scientists Summit, CATL chief scientist Wu Kai said that its second-generation sodium-ion cells can discharge normally even at -40 degrees Celsius, as per several local Chinese media reports. That means EVs with such batteries won't lose range under frigid temperatures, which could help address some of the lingering concerns regarding the extreme weather performance of batteries.

They will launch in 2025 in China, with mass production expected to begin in 2027.

Tesla's 4680 NCM cells present in some newer Model Ys have an estimated energy density of up to 296 watt-hours per kilogram, as per some early teardowns. Sodium-ion batteries are less energy dense. While CATL has not disclosed the energy density of the new cells, it reportedly aims to reach a figure of 200 Wh/kg—a tough goal given that even LFP batteries have only recently hit that mark. That would only be appropriate for low-range EVs or entry-level trims. Some reports also claim that sodium-ion batteries are expected to replace 20-30% of LFP batteries in select applications.

A study published in the U.S. government’s National Library of Medicine calls sodium-ion batteries a “rising star.” Battery giants like CATL, BYD, and Sweden’s Northvolt are already investing in and developing these next-generation cells. So either way, one thing is clear: the future of battery chemistry isn’t headed in a single direction but will likely embrace a mix of chemistries tailored to specific use cases.

In principle, sodium-ion batteries should be cheaper than lithium-ion, because sodium is far more common and far cheaper than lithium (salt is sodium chloride, and the sea is full of it).  But production is still limited, so they are not cheaper yet.  As volumes expand, though, they will fall in cost just as fast as lithium-ion batteries have fallen, cutting battery pack costs to below $35/kWh.  At that price, the average EV battery pack will cost between $2000 and $3000, making EVs cheaper to buy as well as to run than petrol cars.   For reference, in 2010, lithium-ion batteries cost $1392/kWh.  Expect EVs to rapidly move to 100% of all sales, as costs continue to plunge--except of course in the US, where tariffs will stop this happening.  They already make up more than 50% of sales in China, the world's largest car market.  

Because of lower energy density, initially battery-packs will combine sodium-ion and lithium-ion cells.  But cheaper cars, with shorter ranges, will be the first to get 100% sodium-ion batteries.