Lithium-ion batteries continue to gain ground in the rechargeable battery market. However, sodium-ion batteries are simultaneously accelerating their competitive development for large-scale applications (i.e., non-electric vehicles or consumer electronics).
For years, researchers have been working to commercialize sodium batteries. This technology may finally be realized as planned, as two companies have already begun commercial deliveries.
In September 2020, the Department of Energy's Advanced Research Projects Agency (ARPA) awarded Natron Energy, located in Santa Clara, California, $19.9 million as part of a new initiative to rapidly track technologies, an investment aimed at advancing its commercialization efforts. Jack Pouchet, the company's vice president of sales, said the batteries are now in small-batch commercial production. Natron's first customers are data centers and telecommunications companies.
"From a purely performance standpoint, sodium-ion batteries are not attractive for portable electronics or electric vehicles," said KM Abraham, a research professor at Northeastern University and chief technology officer at lithium-ion battery consulting firm E-KEM Sciences. Lithium-ion batteries have a higher energy density than sodium-ion batteries, meaning that the compact lithium-ion batteries can run longer between charges. He said that sodium-ion batteries have so far shown about half the energy density of lithium-ion batteries, reaching 285 Wh/kg.
However, sodium-ion batteries can make lithium-ion batteries more cost-effective in stationary applications, such as renewable energy storage in homes and on the grid, or as backup power for data centers, where cost is more important than size and energy density. Based on currently available information, Abraham expects sodium-ion batteries to cost approximately 10% to 20% less than lithium-ion batteries.
The biggest advantage of sodium batteries is the use of abundant, inexpensive, and benign materials. There is a thousand times more sodium in the Earth's crust than lithium. Extraction and purification are also much cheaper. Furthermore, the sodium metal oxide cathode (the anode, like in lithium-ion batteries, is carbon) typically used in these batteries can be made from a variety of metals, such as iron and manganese. In contrast, lithium-ion cathodes use cobalt, a metal with limited geological reserves and a fragile supply chain centered around a few countries. Other batteries, such as lead-acid and nickel-cadmium, also contain toxic metals. "The main attraction of sodium is sustainability," Abraham said.
Sodium batteries are also more stable and safer than lithium-ion batteries. Pouchet says they have a wider temperature range, are less flammable, and will not experience thermal runaway (which could cause lithium-ion batteries to catch fire) under any circumstances.
Natron is one of the few players developing and commercializing sodium-ion batteries. The company is taking a unique approach, using Prussian Blue, a pigment used in paints and dyes, to manufacture both the cathode and anode. The chemical structure of this low-cost material is exceptionally adept at absorbing and releasing sodium ions, allowing the battery to be charged and discharged in minutes and release energy rapidly. Pouchet says the Prussian Blue electrodes also have a longer lifespan than carbon-based and metal-based electrodes, capable of being charged more than 50,000 times.
Another leading sodium-ion battery company is Faradion from the UK, which has already found markets in Australia and India. Last year, the company announced it had received its first order from investment group ICM Australia for the Australian market, where demand for battery storage in residential, commercial, and grid-scale applications has been growing. They are also developing batteries for commercial vehicles in India.
Faradion states that its prototype battery can provide an energy density of over 140 Wh/kg.
In late February, the company announced a partnership with Phillips 66, an energy company headquartered in Houston, Texas, to develop lower-cost, higher-performance battery anode materials.
Abraham says this targeted research is exactly what the technology needs. In his latest commentary published in ACS Energy Letters, he points out the need for more research into better anode and cathode materials to produce practical sodium-ion batteries with energy densities approaching 200 Wh/kg. He notes promising research underway at the Pacific Northwest National Laboratory, the French National Centre for Scientific Research (CNRS), and the French Electrochemical Energy Storage Research Network. "There's definitely a lot of money going on with sodium-ion batteries," he says.
