Surrey scientists boost sodium-ion batteries by keeping water in material

Surrey scientists boost sodium-ion batteries with water

Researchers at the University of Surrey have found that keeping water inside a key battery material, instead of removing it, dramatically improves the performance of sodium-ion batteries. Their work, published in the Journal of Materials Chemistry A, challenges a long-held manufacturing assumption.

Sodium-ion batteries are seen as a promising, more sustainable alternative to dominant lithium-ion technology. Lithium relies on costly, scarce materials, while sodium is abundant and cheap. The main hurdle has been matching lithium's performance.

Hydrated material outperforms dried version

The team studied a compound called sodium vanadium oxide. Conventionally, this material is heat-treated to remove all water before use in a battery. The Surrey team tested it in its hydrated form, known as nanostructured sodium vanadate hydrate (NVOH).

The hydrated material performed far better. It stored nearly twice as much charge as standard sodium-ion cathode materials. It also charged faster and maintained stability for more than 400 charge cycles.

"Our results were completely unexpected," said lead author Dr. Daniel Commandeur. "People usually heat-treat it to remove the water because it's thought to cause problems. We decided to challenge that assumption."

Breakthrough enables operation in seawater

The researchers made a second major discovery by testing the material in salt water. The hydrated sodium vanadate not only functioned effectively, but it also began removing sodium ions from the water.

A paired graphite electrode simultaneously extracted chloride ions. This dual process is known as electrochemical desalination, suggesting a single system could both store energy and desalinate water.

"This means we might be able to design systems that use seawater as a completely safe, free and abundant electrolyte, while also producing fresh water," Dr. Commandeur said.

Path to cheaper, safer energy storage

The findings could accelerate the development of sodium-ion batteries as a practical alternative. Their advantages over lithium-ion include:

• Lower cost due to sodium's abundance
• Improved safety and reduced fire risk
• A smaller environmental footprint

Potential applications are broad, from grid storage for renewable energy to use in electric vehicles. By simplifying production and boosting performance, this research brings commercially viable sodium-ion batteries a significant step closer.