All-solid-state batteries are often called the future of energy storage.
They are safer and more powerful than today’s lithium-ion batteries, making them attractive for electric vehicles, electronics, and storing renewable energy.
But there’s a catch: most all-solid-state batteries rely on lithium, a metal that is rare, expensive, and environmentally harmful to mine.
Sodium, on the other hand, is abundant, inexpensive, and far less damaging to extract. Scientists have been exploring sodium-based all-solid-state batteries as an alternative.
The problem has been that sodium batteries usually don’t perform well at room temperature, let alone colder conditions.
A research team led by Professor Y. Shirley Meng at the University of Chicago’s Pritzker School of Molecular Engineering has now taken a major step toward solving that problem.
Their study, published in Joule, demonstrates a sodium battery design with thick cathodes that maintains performance at both room temperature and subzero conditions.
“This new research gets us closer to the ultimate goal of producing lithium and sodium batteries side by side,” said Prof. Meng. “It’s not about replacing lithium. We need both.”
The breakthrough came from stabilizing a “metastable” structure of a compound called sodium hydridoborate.
Normally, this structure is too unstable to exist at room temperature, but the researchers found a way to lock it in place. By heating the compound until it began to crystallize and then rapidly cooling it, they were able to preserve the structure.
This approach is a common technique in materials science, but it had never been applied to solid electrolytes for batteries.
The result was a form of sodium hydridoborate with extremely high ionic conductivity—up to 1,000 times higher than its original state. That makes it much more effective for moving sodium ions back and forth inside the battery, a critical requirement for reliable performance.
Because the method is already well established, it could be easier for industry to adopt compared to more experimental techniques.
“Since this technique is established, we are better able to scale up in the future,” explained first author Sam Oh, who carried out the work as a visiting scholar in Meng’s lab.
The team paired this metastable electrolyte with a specially coated O3-type cathode.
Crucially, they made the cathodes thick, which increases the amount of active material and boosts the battery’s theoretical energy density. In simpler terms, a thicker cathode allows the battery to store more energy in the same space.
The result is a sodium-based all-solid-state battery design that outperforms earlier versions and works across a wider temperature range.
“It’s still a long journey, but this research helps open up the opportunity for sodium to stand alongside lithium in powering the future,” Oh said.
