European battery manufacturer Northvolt, in collaboration with Swedish company Altris, claims to have developed a sodium-ion battery. These pouch cells boast an energy density of 160 Wh/kg, akin to the typical energy density of LFP batteries five years ago and comparable to other sodium-ion batteries from China. The cathode material used is Prussian White. In 2021, Chinese manufacturer CATL introduced similar battery cells with equivalent energy density specifications.
These batteries, owing to their battery chemistry, entirely eliminate critical battery materials such as lithium, nickel, cobalt, and graphite. Additionally, they forego the use of copper. The cathode material, referred to as Prussian White, comprises sodium hexacyanoferrate, a chemical compound akin to the dye Prussian Blue, made from sodium, iron, carbon, and nitrogen. Instead of graphite, the anode employs hard carbon derived from biomass and other carbon compounds, requiring less energy for extraction compared to graphite.
The cathode material is manufactured by Swedish company Altris, operating a pilot plant capable of producing approximately 1 GWh of battery capacity per year. While no specifics were provided about the origin of the anode material, it is likely sourced from Stora Enso, a Swedish-Finnish paper manufacturer producing hard carbon from lignin. Lignin, previously discarded as waste during paper production, is separated from wood into pulp and lignin using caustic soda.
Industrial-scale production likely won’t commence before 2025
Unlike lithium, sodium doesn’t alloy with aluminum at room temperature, allowing the use of conductor foils in the anode. In a lithium-ion battery, these foils would quickly deteriorate.
This approach saves weight and costs. Aluminum, in terms of weight, conducts electricity twice as effectively as copper. Additionally, aluminum ores have 25 to 50 times higher metal content than copper ores, significantly reducing environmental damage associated with their production.
The energy density specifications provided for the pouch cells are not directly comparable to the usual cylindrical or prismatic cells, which are constructed with stable metal casings.
In practice, multiple pouch cells are stacked and housed within metal casings, slightly reducing the overall system’s energy density. Northvolt, however, is already developing sodium-ion batteries with higher energy densities and different battery chemistries primarily intended for use in electric vehicles.
Northvolt did not disclose specific plans regarding the timing, location, or scale of production. Typically, the industrialization of production for a fully developed battery cell takes around 2 to 3 years. Consequently, Northvolt could become the first manufacturer outside of Asia to produce sodium-ion batteries on a large scale by 2025.
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