There are many questions surrounding the current state of sodium-ion batteries. For most, the news that CATL plans to commercialize sodium-ion batteries for electric vehicles by 2026, offering a 310-mile range, is unexpected.
Sodium-ion batteries, like lithium-ion batteries, feature a variety of cathode chemistries. Lithium-ion batteries are typically named after their metal oxide cathodes, while their anodes are primarily graphite, a highly ordered carbon form. Lithium electrolytes usually consist of an organic solvent such as ethylene chloride combined with a lithium compound. In contrast, sodium-ion batteries use a sodium compound and their own solvent selection. Some research is also exploring the replacement of liquid electrolytes with solid ones, though this has not yet become mainstream.
To understand the progress, let’s review previous sodium-ion batteries from several companies. This provides perspective before examining CATL’s latest announcement. CATL previously achieved 160 Wh/kg using a Prussian white cathode and hard carbon anode, with a 15-minute charge to 80% and over 90% capacity retention at -20°C. This design enabled a system integration efficiency of 80% at the pack level.
Faradion, using a layered oxide cathode and hard carbon anode, reached 155 Wh/kg, a similar temperature range, and a 3,000-cycle life. Tiamat, with a polyanion cathode and hard carbon, achieved 90–120 Wh/kg and 5,000 cycles. Natron, using Prussian blue for both cathode and anode, delivered 20–30 Wh/kg and a 25,000-cycle life from -20°C to 40°C. Early HiNa cells, using hard carbon, reached 111 Wh/kg and 248 Wh/l.
Battery chemistries vary widely in performance. Comparisons depend on the choice of anode, cathode, and electrolyte. Sodium-ion batteries generally operate across a wider temperature range, from -40°C to 70°C with 90% retention, while lithium batteries lose capacity rapidly below -10°C and become non-operational at -40°C, especially LFP types. Only lithium titanate (LTO) among lithium batteries achieves 10,000 cycles or more. Sodium-ion batteries are more fire-resistant than lithium-ion batteries, tolerate voltage fluctuations better, and can be fully discharged to zero volts. Some sodium-ion batteries operate without a battery management system, which is impossible for lithium batteries due to risks of fire or permanent failure from over- or under-voltage. In safety tests, sodium-ion batteries withstand temperatures of several hundred degrees Celsius before burning.
LFP batteries are more fire-resistant than NMC but not as much as sodium-ion batteries. Recent strict Chinese government safety standards for fire and explosion are met by CATL’s Naxtra sodium-ion batteries, effectively excluding NMC from consideration.
In 1980, Newman demonstrated reversible sodium-ion transfer in titanium disulfide (TiS2). Despite this, most focus shifted to lithium-ion batteries, which achieved commercial success in 1991 with Sony’s lithium-cobalt cells.
Sodium-ion development advanced with the discovery that hard carbon could serve as an anode. In 2000, D. A. Stevens and Jeff Dahn identified glucose-based hard carbon as a viable anode. After 2010, research into sodium-ion chemistries accelerated. Faradion was founded in 2011, HiNa launched products in 2017, and by the 2020s, companies like Faradion, Natron, Northvolt, HiNa, Tiamat, Farasis, and Alsym joined the field, with CATL and BYD adding sodium-ion batteries to their portfolios.
Sodium-ion batteries have been available since 2017, but most attention was on NMC chemistries. Sodium-ion performance improved rapidly, with first-generation batteries offering 100 to 140 Wh/kg and up to 290 Wh/l, suitable for energy storage and e-bikes. These early batteries, using hard carbon, found success even in small cars.
HiNa and others made progress in energy storage, where low energy density is less critical. The competitive Chinese market, led by CATL and BYD, spurred further sodium-ion development. Large research teams accelerated advancements.
As sodium-ion chemistry improved, LFP batteries also advanced, challenging NMC at the entry level by increasing cell density and improving pack volume efficiency. The first Tesla LFP packs used Blade battery cells with 166 Wh/kg and 365 Wh/l, achieving a pack density of 125 Wh/kg and a cell-to-pack mass ratio of 74%.
Researchers discovered that sodium-ion batteries could be produced using existing manufacturing equipment and techniques. With lower material costs, sodium-ion batteries could match LFP performance at a reduced price. HiNa claims its sodium-ion batteries are 30 to 40% cheaper than lithium equivalents, mainly due to material cost advantages. CATL expects sodium-ion batteries to capture 50% of the LFP market. Many strategies used to enhance lithium performance can be applied to sodium-ion, quickly boosting its capabilities. Sodium-ion chemistry also offers low volatility, high cycle life, and a wide temperature range. Techniques to improve lithium energy density are now being used to enhance sodium-ion batteries. The previous generation of sodium-ion batteries was already gaining attention for energy storage and was close to meeting EV requirements. Sodium-ion technology has been developing steadily, but only recently reached a level that commands broader attention.
CATL chose sodium-ion chemistry for its resource availability, cost, and supply stability. As battery production scales up, reliable sources of abundant, low-cost materials become crucial. Sodium-ion materials are widespread and less susceptible to price swings or supply disruptions than graphite, nickel, lithium, or cobalt. Lithium carbonate prices have been volatile, pushing sodium-ion technology forward. Sodium-ion resources like sodium carbonate and hard carbon are abundant and reliable.
Second-generation sodium-ion batteries feature several innovations. CATL announced self-forming anodes, which are thin layers of sodium deposited directly on the conductor, rather than thick hard carbon layers. Naxtra offers 60% higher volumetric density than CATL’s first-generation sodium-ion battery. Earlier research suggested volumetric densities of up to 400 Wh/l were possible. Unigrid sodium-ion batteries have achieved 178 Wh/kg and 417 Wh/l in full pouch cells, demonstrating the technology’s potential. Naxtra, at 175 Wh/kg, already surpasses the 166 Wh/kg of the first LFP Tesla batteries and may match their volumetric energy density.
CATL’s patents reveal further developments, such as using antimony to reduce moisture effects and reinforce the cathode matrix, enabling cheaper water-based production. These improvements also flatten the discharge curve, making the battery more suitable for EVs. Unigrid’s proprietary methods also achieve a flatter discharge curve.
Recently, the world’s first production solid-state battery was announced by Donutlabs. They emphasize that it is not a lithium battery and is made from widely available materials, suggesting it is sodium-ion. This aligns with expectations for sodium-ion solid-state batteries. Some confusion exists about solid-state technology, but it refers to the electrolyte, not the battery chemistry. For example, NMC-SSB would be a nickel manganese cobalt solid-state battery. Batteries consist of a cathode, anode, and electrolyte. Until now, all batteries used liquid electrolytes, while the anode and cathode are solid. Sodium-ion batteries are not typically named by their cathodes, but there are three main types: polyanion, layered oxide, and Prussian blue analogs. Batteries could be classified by cathode, anode, and electrolyte.
CATL’s Naxtra demonstrates that sodium-ion batteries are advancing faster than anticipated. With advantages in cost, greener manufacturing, safety, cycle life, temperature range, and supply stability, CATL is ready to begin large-scale sodium-ion production for EVs and other applications. Performance improvements now put sodium-ion batteries in direct competition with LFP, making them suitable for EVs as CATL has announced. CATL expects sodium-ion batteries to deliver over 300 miles of EV range, even in cold conditions. As production scales, lower material costs will further increase sodium-ion’s cost advantage.
CATL’s first-generation sodium-ion batteries improved gravimetric energy density by 9%, while self-forming anodes in the second generation increased volumetric density by 60%. This suggests volumetric energy density has risen from 290 Wh/l to 350 Wh/l, matching or exceeding the levels used in high-volume EV Blade battery packs. There is no reason to believe Naxtra’s volumetric energy density is lower than some LFP Blade batteries, especially since it exceeds LFP in Wh/kg. As battery costs decrease, new applications such as electric ships and expanded renewable energy storage will drive further production growth. CATL’s plans for electric shipping indicate that volume production will lower costs enough to support these uses within three years, with further performance improvements likely to follow and continue the cycle of advancement.
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