Solid-state sodium batteries could be safer, cheaper, more powerful option

We rely on batteries now more than ever, from our phones and laptops to electric vehicles. But the ones powering today’s technologies aren’t without their shortcomings. They can be expensive, flammable, and they rely on increasingly in-demand materials that must be mined and processed.

Researchers at Western University are working on a new type of battery—called solid-state sodium batteries—that show considerable promise in addressing these challenges.

“Right now, most of the batteries we use contain flammable liquid electrolytes and rare elements like lithium,” says Dr. Yang Zhao, professor in the Department of Mechanical and Materials Engineering at Western. “Sodium is much more abundant and cheaper, and if we can make it work in a solid-state form of the electrolyte, it could be cheaper, safer, and long lasting.”

Solid-state electrolytes replace the flammable liquids in conventional batteries with solid materials. These solids are inherently safer and promise higher energy density, meaning batteries last longer between charges. But getting the sodium ions to move quickly and reliably through solids has been a tough scientific puzzle.

Zhao and colleagues formulated a new material that contains sulfur and chlorine. While traditional electrolytes are chemically stable, they tend to move sodium ions poorly from the positive end of the battery to the negative. The sulfur component in the new design boosts conductivity by making it easier for ions to hop through the structure, and strengthens the material overall. They published their findings in the journals Advanced Functional Materials and Advanced Materials.

In addition to its high sodium-ion conductivity, the material developed by Zhao and his team has excellent thermal and mechanical stability. This is a big deal for batteries that need to last for countless charge-discharge cycles and perform reliably across a wide temperature range. In many solid-state designs, the electrolyte can degrade when it comes in contact with other battery components. That’s not the case with the material developed by the team at Western.

Zhao and his colleagues used the powerful X-rays of the Canadian Light Source (CLS) at the University of Saskatchewan to observe how ions move inside the solid electrolyte.

“These X-ray tools allow us to see the local chemical environment, ion pathways, and bonding structures in ways that regular lab instruments can’t,” said Zhao. “They’re absolutely essential for developing solid-state battery materials.”

While solid-state batteries are likely still a few years away from widespread commercial use, Dr. Zhao is optimistic. “We’re making real progress toward safer, more cost-effective batteries,” he said.