A popular sodium-ion battery designed by the company Hina and used in cars and large-scale energy storage systems in China matches performance parameters and production quality of Tesla's lithium-ion batteries, finds new research published in Cell Reports Physical Science.
Once the Hina battery is tweaked to charge more effectively at low temperatures and function better at high energy densities, it could provide a cost-effective alternative for future electric vehicle batteries that depend on sodium—an abundant and easily sourced material—instead of lithium.
"The combination of good uniformity, high power capability, and strong low-temperature performance makes these cells attractive for stationary storage, grid services, and shorter-range or commercial vehicles where potential lower cost and resource availability matter more than maximum driving range," says Moritz Schütte, a battery researcher at RWTH Aachen University in Germany.
How the Hina cells were tested
To assess how Hina batteries compare to more advanced Tesla batteries, Schütte's team used a non-destructive technique called impedance spectroscopy to measure the uniformity of 120 sodium-ion battery cells.
Next, to map out the power and energy performances of individual cells under real-life conditions, the team tested the batteries at varying currents and at temperatures from −20 °C to 45 °C. They also used X-rays to see the battery's internal structure, then opened up the cells to measure their electrode dimensions, compositions, and microstructures.
They found that the battery uses a tabless, a double-aluminum current collector design that reduces resistance and ensures a uniform temperature distribution—and also mirrors the current design of Tesla batteries.
"We were positively surprised by how uniform the cells are," says Schütte.
Current drawbacks and future improvements
However, the sodium-ion battery has some limitations when it comes to energy density and charging at low temperatures. "The high-power performance was better than one might expect from an early commercial sodium-ion product," says Schütte.
"However, for applications that require frequent charging at low ambient temperatures, appropriate thermal management or operating strategies will be important because low-temperature charging remains a clear weakness."
The researchers also found unexpectedly high, unevenly distributed levels of copper in certain cathode regions of the battery, which "raises interesting questions about its role in performance and aging," said Schütte. "It will be exciting to see future sodium-ion technologies that are free of nickel and copper, as well, while achieving competitive energy density."
Since sodium is much more abundant and widely available than lithium, using it for batteries could cut raw material costs for manufacturers and reduce long-term supply chain risks. Sodium-ion batteries also perform well under load at low temperatures, making them an appealing option for both stationary power storage and mobile applications in cold climates.
"However, today's commercial sodium-ion cells generally have lower energy density than the best lithium-ion cells, and the technology is less mature overall," said Schütte.
Next, the authors plan to better understand and improve upon the battery's charging capabilities at low temperatures so that they can charge more safely and efficiently below 0 °C. Further research should also focus on optimizing the materials used to make sodium-ion batteries, added Schütte.
"Advances in hard-carbon anodes and electrolyte formulations may be especially promising," he said.
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