Sodium-ion solid-state could solve range and cost issues

Battery production is still the most expensive part of electric vehicle (EV) production. Between the sourcing of raw materials, establishing supply chains and building battery cell plants, it is difficult for EVs to close the price gap with their internal combustion engine (ICE) counterparts. At the same time, affordability is the primary barrier to EV adoption. Despite Tesla’s promise to deliver a US$25,000 EV by 2025, it has yet to reveal any such vehicle or provide details on how to turn a profit at this price point.

At present, the most widely used battery chemistry is lithium-ion. The cost of producing these batteries declined almost one-third in 2023 due to a decrease in the price of lithium, but it hasn’t been enough to meaningfully lower EV prices. In addition to cost, lithium faces ethical sourcing challenges. Much of the world’s supply of battery-grade lithium comes from Democratic Republic of the Congo, where child labour is an ongoing concern. The lithium supply chain is also vulnerable to geopolitical instability. China, which has an oligopoly over the refinement process, is currently embroiled in trade disputes with both the US and the EU.

Finding an alternative to lithium-ion may prove critical to ensuring that Western automakers can produce EVs at scale and at prices low enough for the mass market. An alternative chemistry—sodium-ion—has existed for decades. However, due to its comparatively low energy density, it has largely been dismissed as viable only for micromobility or stationary storage use cases.

This could soon change. TaiSan, one of a growing number of start-ups taking an interest in sodium-ion technology, believes it can achieve an energy density of 300Wh/kg through its proprietary quasi solid-state sodium-ion battery technology. If it can realise this goal, the company could potentially offer superior performance to most lithium-based batteries currently on the market.

Overcoming the range deficit

“Our mission is to increase energy density, and sodium-ion is not good enough for EVs just yet,” Sanzhar Taizhan, Founder and Chief Executive of TaiSan, tells Automotive World. “Because most automakers require more than 200Wh/kg, we need to improve the technology to make it commercially viable.” TaiSan has not publicly disclosed the energy density metrics of its first-generation prototypes, but it is unlikely the company has been able to produce a commercially viable battery that surpasses this density level. However, Taizhan notes that progress is moving faster than “initially expected.”

To date, Chinese automaker JAC Yiwei is the only automaker selling EVs containing sodium-ion batteries to customers. Its Huaxianzi hatchback has been shipped to an undisclosed number of customers in China, as well as 5,000 intended for export to Latin America. The battery’s energy density is 140Wh/kg, enabling a limited maximum range of 210km.

TaiSan is confident that successive refinements to its quasi solid-state approach will enable the company to surpass 200Wh/kg and come closer to the desired 300Wh/kg. The difference between its approach and “full” solid-state lies in the use of a small amount of liquid electrolyte alongside the solid material. “Typical solid-state uses ceramics, sulfides or polymers, but we have a gel-type material,” remarks Taizhan. “This allows us to have the advantages of solid-state, like increased performance, without some of the drawbacks.”

One benefit is a reduction in the number of dendrites that form on the anode and could potentially lead to short circuits. It also mitigates the need for high temperatures to achieve the desired level of ionic conductivity and lowers stacking pressure, which in turn reduces weight. Crucially, it will allow sodium to become competitive with other technologies in terms of range. While it will likely never reach parity with lithium- or nickel-based solid-state architectures, it does allow sodium-ion to overcome its performance deficit relative to traditional liquid-based batteries.

A broader case

Overcoming this performance deficit would have little upside if there were no additional benefits to sodium-ion technology. From the consumer’s perspective, the primary benefit is reduced cost. “If you want to put a US$20,000 car on the market, then you really need a battery that costs no more than US$4,000,” remarks Taizhan. “Automakers have found it difficult to turn a profit on cheaper cars, which is why we have so many premium models in the EV segment.” When brought to moderate scales, TaiSan believes its batteries will cost roughly 20% less than incumbent solutions.

These cost advantages come primarily from the abundance of sodium relative to rare earth minerals like lithium. Sodium is 1,000 times more abundant in the Earth’s crust than lithium and also more widely distributed. “More than 90% of natural sodium is located in the US because of soda-lime glass production in the 1950s,” Taizhan remarks. By contrast, much of the sodium in Asia is produced with coal and would be difficult to justify in terms of sustainability. Given the ease of establishing short supply chains, sodium batteries would likely appeal to Western automakers and governments looking to decouple themselves from China. Local supply chains would also allow eliminate ethical concerns around the use of child labour in metal sourcing.

Another consumer benefit is less vehicle downtime. While it may have shortcomings in terms of energy density, sodium-ion is capable of faster charging speeds than lithium-ion: the Huaxianzi hatchback can go from 10% to 80% state of charge in less than 15 minutes. Taizhan emphasises that these charging speeds will be exponentially faster in a solid-state scenario.

Building your own factory is fancy to say, but it’s nearly impossible for us in terms of cost

Despite the apparent promise, Taizhan is quick to emphasise that sodium-ion remains largely unproven at commercial scales. While he believes it can and should be made to work, TaiSan’s research and development around the technology remains at a relatively early stage. In July 2024, the company raised £1.3m (US$1.7m) in a funding round to build prototypes—first for internal testing, then for shipping to customers for their own testing. It has secured seven memorandums of understanding with battery manufacturers for when its solid-state technology receives approval for commercial vehicles.

“Building your own factory is fancy to say, but it’s nearly impossible for us in terms of cost,” Taizhan concludes. “Rather, our goal is simple: we want to validate sodium-ion technology and then use existing production lines to bring it to the mainstream.”