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

We now rely on batteries more than ever before, from our phones and laptops to our electric cars. However, the underpinnings of today’s technology are not without their drawbacks. They rely on expensive, highly flammable, and in-demand materials that must be mined and processed.

Researchers at Western University are working to develop a new type of battery called an all-solid-state sodium battery that shows great promise in addressing these challenges.

“Most of the batteries we use today contain flammable liquid electrolytes and rare elements such as lithium,” says Dr. Yang Zhao, a professor in Western University’s Department of Mechanical and Materials Engineering. “Sodium is much more abundant and cheaper, and if we can make it work in solid electrolyte form, it could be cheaper, safer and last longer.”

Solid electrolytes replace the flammable liquid in traditional batteries with solid materials. These solids are inherently safe and promise higher energy density, which increases battery life between charges. However, moving sodium ions quickly and reliably through solids has been a difficult scientific puzzle.

Zhao et al. formulated a new material containing sulfur and chlorine. Although traditional electrolytes are chemically stable, sodium ions tend to have a hard time moving from the positive to the negative electrode of a battery. The sulfur content in the new design increases electrical conductivity by making it easier for ions to pass through the structure, strengthening the overall material. They published their findings in the journals Advanced Functional Materials and Advanced Materials.

The material developed by Zhao and his team has excellent thermal and mechanical stability in addition to high sodium ion conductivity. This is a big problem for batteries, which must withstand countless charge-discharge cycles and operate reliably over a wide temperature range. In many solid-state designs, the electrolyte can degrade if it comes into contact with other battery components. This is not the case with the materials developed by Western’s team.

Zhao and his colleagues used powerful X-rays from the University of Saskatchewan’s Canada Light Source (CLS) to observe how ions move within a solid electrolyte.

“These X-ray tools allow us to observe local chemical environments, ion pathways, and bond structures in a way that is not possible with regular laboratory equipment,” Zhao said. “It is essential for the development of all-solid-state battery materials.”

Although solid-state batteries may still be years away from widespread commercial use, Dr. Zhao is optimistic. “We are making real progress toward developing safer and more cost-effective batteries,” he said.