[Complete Battery Mastery](21) "Unfazed at -20℃" Sodium Battery, a 'Game Changer' or 'DoA'?

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Recently, a polar vortex hit the United States, causing electric vehicles with depleted batteries to be stranded and unable to move. Charging stations experienced a charging crisis. Lithium-ion batteries, whose discharge efficiency drops sharply in extreme cold, have become another factor causing hesitation in purchasing electric vehicles. It is known that lithium-ion batteries reduce driving range by about 20% in winter.

A new secondary battery with strong low-temperature performance is now being commercialized. It is the sodium-ion battery. Sodium-ion batteries exhibit 90% discharge efficiency even in harsh environments as low as minus 20 degrees Celsius. Moreover, they are cheaper than lithium-ion batteries. The biggest drawback is their lower energy density.

China and India are actively advancing sodium-ion battery development. Recently, Europe and the United States have also recognized the potential of sodium-ion batteries and are increasing investments. There are opinions that they should not be dismissed as merely 'cheap Chinese batteries.'

On the other hand, some analyses suggest that the recent plunge in lithium prices has erased the price advantage of sodium-ion batteries. There are even gloomy forecasts that they will be 'Dead on Arrival (DoA).' Which view is correct will soon be determined.

Are batteries really made from real salt?

Sodium-ion batteries refer to secondary batteries that use sodium as the main material in the cathode. Sodium is expressed as Sodium in English, derived from Soda. Therefore, sodium-ion batteries are also called Sodium-ion Batteries (SiB).

Sodium (Na), atomic number 11 on the periodic table, is an alkali metal belonging to Group 1 along with lithium (Li), atomic number 3. Because it easily ionizes by losing one electron, it shares characteristics similar to lithium and has long been studied as a secondary battery material. The structure and operating principle of sodium-ion batteries are also similar to lithium-ion batteries, allowing existing manufacturing processes to be utilized.

The biggest advantage of sodium-ion batteries is their price. They are predicted to be about 20-40% cheaper than lithium-ion batteries. Some analyses suggest production costs could be as low as one-third of lithium-ion batteries.

Wood Mackenzie, an energy market research firm, estimated that if layered oxides are used in the cathode, the price of sodium-ion batteries could drop to $123 per kilowatt-hour (kWh), and if Prussian white is used, it could go down to $90 per kWh.

UK market research firm IDTechEx evaluated that the average price of sodium-ion batteries will be around $87 per kWh. If iron and manganese are used, the price is expected to fall to $40/kWh by 2030. This is about 28% cheaper than the 2023 average price of lithium-ion batteries at $139/kWh.

The reason sodium-ion batteries can achieve such low prices is the ease of obtaining raw materials. Sodium is much more abundant and cheaper than lithium. Sodium is the sixth most abundant element on Earth, making up about 2.6% of the Earth's crust. It can be easily extracted from seawater or rock salt. Additionally, sodium reacts well with aluminum, allowing the use of aluminum as the anode current collector instead of expensive copper.

Image courtesy of Wood Mackenzie

Sodium-ion batteries use Prussian white, layered oxides, and polyanions as cathode active materials. Since they do not require cobalt or nickel used in lithium-ion batteries, this also helps reduce costs.

Sodium-ion batteries have better low-temperature characteristics compared to lithium-ion batteries. Research shows that sodium-ion batteries maintain 90% capacity even at minus 20 degrees Celsius. In contrast, lithium-ion batteries degrade to about 60-70% capacity under the same conditions.

Comparison of Sodium-Ion Battery Characteristics. Image courtesy of IDTechEx

However, there are limitations. Sodium-ion batteries have faced challenges in commercialization due to several constraints.

First, sodium atoms are heavier and larger than lithium, which is disadvantageous for energy density. Sodium's atomic weight is 23g/mol, about 3.3 times that of lithium (6.9g/mol). Also, sodium's standard reduction potential is -2.7 volts (V), which is 0.3V higher than lithium's -3V. This results in inherently lower energy density (= voltage × capacity/weight).

The currently developed sodium-ion batteries have an energy density of about 140-160 watt-hours per kilogram (Wh/kg), which does not match lithium iron phosphate (LFP) or ternary batteries. Recently, research to increase energy density by changing cathode material composition is actively underway. China's CATL has set a goal to raise energy density to around 200 Wh/kg.

Sodium-ion batteries have difficulty using graphite as the anode. Lithium ions have a size of 0.076 nanometers (nm), allowing easy insertion and extraction between graphite layers (0.34 nm). In contrast, sodium ions are 0.102 nm, making insertion reactions in graphite layers less favorable.

Image source=Journal of Polymer Science and Technology Vol. 30, No. 5 (2019.5)

As an alternative, sodium-ion batteries often use hard carbon (0.37 nm), which has a wider interlayer structure than graphite, as the anode. However, hard carbon is more expensive and has lower energy capacity than graphite.

There is debate about the safety of sodium-ion batteries. Some claim sodium-ion batteries are safer than lithium-ion batteries, but this has not yet been verified.

A 2023 report titled "Exploration of future battery types and safety" by The Netherlands Institute for Public Safety found that sodium-ion batteries also exhibit thermal runaway phenomena similar to lithium-ion batteries. However, thermal runaway progresses more slowly in sodium-ion batteries.

Sodium is also a highly reactive and unstable material that is difficult to handle. When sodium meets water, it generates high heat and hydrogen gas (2Na + 2H2O → 2NaOH + H2), causing explosions. Sodium metal is stored in kerosene to prevent contact with air.

Emerging Market... China Already Commercialized

China leads in sodium-ion battery research and commercialization.

China's largest battery company, CATL, announced in 2021 that it would develop and produce sodium-ion batteries as next-generation batteries. Until then, sodium-ion batteries were considered unsuitable for electric vehicles due to their weight and low energy density. However, with the surge in lithium prices at that time, the cheaper sodium-ion batteries gained attention. CATL introduced a first-generation sodium-ion battery with 160 Wh/kg and announced plans to develop a second-generation battery with 200 Wh/kg performance.

CATL's Sodium-ion Battery

The world's largest electric vehicle manufacturer, BYD, has also started developing sodium-ion batteries. On January 4, BYD held a groundbreaking ceremony for a sodium-ion battery plant in Suzhou. BYD plans to invest about 10 billion yuan (approximately 1.86 trillion KRW) to establish an annual production capacity of 30 gigawatt-hours (GWh). Earlier, BYD's subsidiary, FinDream Battery, signed a contract with three-wheeler company Huaihai to build a sodium-ion battery factory. BYD's sodium-ion batteries are expected to be installed in two- and three-wheelers and small electric vehicles.

BYD is holding a groundbreaking ceremony for a sodium-ion battery factory in Suzhou. Photo by Suzhou Government

Some have already commercialized. Chinese automaker JAC announced on December 27 that it began production of the first vehicle equipped with sodium-ion batteries in China. This vehicle is scheduled for delivery starting late January this year. It is equipped with a 25 kWh battery and can travel 252 km on a single charge. The cell-level energy density is 140 Wh/kg.

The vehicle uses 32140 cylindrical batteries from Haina Battery, headquartered in Beijing, China. Haina Battery was established in 2017 by the Chinese Academy of Sciences' Institute of Physics and has long researched sodium-ion batteries. JAC's parent company, JAG, was established with 50% investment each from the Chinese government and Volkswagen.

JAC's sodium-ion battery electric vehicle 'Yiwei-3'. Photo by JAC

India is also showing serious interest in sodium-ion batteries.

India's largest conglomerate, Reliance, acquired 100% of UK-based Faradion for about 100 million pounds in December 2021. Founded in 2011, Faradion is known for having top-level technology in this field. In December 2022, Faradion announced the installation of its first sodium-ion battery in New South Wales, Australia.

Aragon Institute, the birthplace of NCM, also files patents

Not only Asia but also Western countries are paying attention to the potential of sodium-ion batteries and are entering the market one after another.

On January 8, the Argonne National Laboratory under the U.S. Department of Energy (DOE) announced that it developed a new cathode material for sodium-ion batteries to replace lithium-ion batteries and registered a patent. The lead researcher was Senior Scientist Christopher Johnson, who, along with Michael Thackeray and Karil Amin, developed nickel manganese cobalt (NCM) cathode materials.

Christopher Johnson, a researcher at the Argonne National Laboratory in the United States, is developing next-generation batteries in the laboratory. Photo by Argonne National Laboratory

The research team developed a nickel manganese iron (NMF) sodium-ion battery cathode material derived from NCM cathode materials. Argonne explained that after more than 10 years of sodium-ion battery research, they developed a layered structured cathode material. They emphasized that the battery is inexpensive because it does not use cobalt in the cathode. This battery can travel 180-200 miles (289-321 km) on a single charge.

Sweden's Northvolt announced in November 2023 that it developed a sodium-ion battery with an energy density of 160 Wh/kg. This battery is pouch-type, using Prussian white for the cathode and hard carbon for the anode.

Sodium-ion battery developed by Northvolt, Sweden. Photo by Northvolt

Northvolt stated, "We will be the first to produce and commercialize batteries based on Prussian white." The company emphasized that it uses abundant minerals such as sodium and iron and does not use lithium, nickel, cobalt, or graphite. They highlighted that this reduces dependence on China compared to lithium-ion batteries from a supply chain perspective.

France's Tiamat plans to build a sodium-ion battery plant with an annual production capacity of 5 GWh by 2029. The first phase will construct a 700 megawatt-hour (MWh) plant by 2025. Tiamat is a sodium-ion battery specialist spun off from the French National Center for Scientific Research (CNRS). The company also attracted investment from multinational automaker Stellantis in January.

In South Korea, research and development (R&D) on sodium-ion batteries is not very active. Among private companies, Energy11 is developing sodium-ion battery cells. Aekyung Chemical produces hard carbon used as an anode material for sodium-ion batteries.

Lithium prices plummet...

Outlooks on sodium-ion batteries are mixed. The domestic industry largely expects the market to be limited to two-wheelers, small vehicles, and energy storage systems (ESS) due to the weight and low energy density of sodium-ion batteries. Geographically, the market is expected to be confined to China, India, and Southeast Asia.

This is also why domestic battery companies have not paid much attention to sodium-ion batteries. They lack the manpower and resources to develop sodium-ion batteries alongside other priorities. In contrast, Chinese companies had sufficient incentives to develop and produce sodium-ion batteries even considering only their domestic market. Chinese battery companies also seem to be targeting nearby Southeast Asian markets.

The recent plunge in lithium prices also darkens the outlook for sodium-ion batteries. If lithium-ion battery prices fall further, the biggest advantage of sodium-ion batteries?their price competitiveness?will diminish.

As of January 2024, lithium is trading at about 80% lower prices compared to 2022 in the international commodity market. Bloomberg NEF expects lithium-ion battery prices to fall below $100/kWh by 2027. If battery prices drop below $100/kWh, the production cost of electric vehicles will be comparable to conventional internal combustion engine vehicles.

However, with recent interest from U.S. and European companies in sodium-ion batteries, some are optimistic about their establishment. Especially given the high Chinese dependence on lithium, nickel, cobalt, and graphite?the main raw materials for current lithium-ion batteries?sodium-ion batteries, which use cheaper and more abundant materials, could be a viable alternative. The Korean government also started supporting sodium-ion battery research this year.

Market research firms have also released optimistic forecasts for sodium-ion batteries. IDTechEx predicts that about 10 GWh of sodium-ion batteries will be used by 2025. Afterward, it expects an average annual growth rate of 27%, with usage reaching 70 GWh by 2033.

SNE Research forecasts that sodium-ion batteries will be produced at least 11% and up to 24% cheaper than LFP by 2035, with market demand reaching up to 254 GWh by 2035. In terms of value, this corresponds to an annual market size of $14.2 billion (about 19 trillion KRW).

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Eugene Investment & Securities, Will Sodium-ion Batteries Become a Game Changer?, 2023.2.24
electrive, Reliance takes over Faradion for ?100 million, 2022.1.18
IDTechEx, Sodium-Ion Batteries Will Diversify the Energy Storage Industry, 2023.1.10
Wood Mackenzie, Sodium-ion batteries: disrupt and conquer?, 2023.2.21
IDTechEx, Home Technologies Research Highlights Cheaper and Safer Sodium-Ion Batteries on the Horizon, 2023.7.14
PV Magazine, Sodium-ion battery fleet to grow to 10 GWh by 2025, 2023.7.17
Fraunhofer ISI, Alternative Battery Technologies Roadmap 2030+, 2023.9
The Netherlands Institute for Public Safety, Exploration of future battery types and safety, 2023.10.16
Power Technology, Sweden’s Northvolt makes breakthrough in sodium-ion battery technology, 2023.11.22
Inside EVs, Are Sodium-Ion Batteries Dead On Arrival? An Expert Weighs In, 2023.12.3
Car News China, BYD starts construction of 30 GWh sodium-ion battery plant in China, 2024.1.5
ARGONNE NATIONAL LABORATORY, Cathode innovation makes sodium-ion battery an attractive option for electric vehicles, 2024.1.8