Sodium-ion batteries are considered one of the most promising sustainable alternatives to lithium-ion technology, which relies on expensive and environmentally harmful materials. Sodium is plentiful and inexpensive, but achieving comparable performance has long been a challenge.
In their new study, published in the Journal of Materials Chemistry A, the Surrey team found that a common sodium-based compound - sodium vanadium oxide - performs far better when its natural water content is preserved. The resulting material, called nanostructured sodium vanadate hydrate (NVOH), stored nearly twice the charge of typical sodium-ion materials, charged more quickly, and maintained stability over 400 charge cycles.
"Our results were completely unexpected," said Dr Daniel Commandeur, Research Fellow at the University of Surrey School of Chemistry and Chemical Engineering and lead author of the study. "Sodium vanadium oxide has been around for years, and people usually heat-treat it to remove the water because it's thought to cause problems. We decided to challenge that assumption, and the outcome was far better than we anticipated. The material showed much stronger performance and stability than expected and could even create exciting new possibilities for how these batteries are used in the future."
The researchers also demonstrated that NVOH can operate efficiently in salt water, where it removed sodium ions while a graphite electrode simultaneously extracted chloride ions - a process known as electrochemical desalination.
"Being able to use sodium vanadate hydrate in salt water is a really exciting discovery," Dr Commandeur added. "It shows sodium-ion batteries could do more than just store energy - they could also help remove salt from water. In the long term, that means we might be able to design systems that use seawater as a completely safe, free and abundant electrolyte, while also producing fresh water as part of the process."
This advance could help drive sodium-ion batteries toward large-scale, low-cost deployment, supporting the transition to greener energy storage systems. By simplifying production and eliminating reliance on lithium, the approach offers a sustainable path for applications ranging from renewable grid storage to electric vehicles.
Research Report:Nanostructured sodium vanadate hydrate as a versatile sodium ion cathode material for use in organic media and for aqueous desalination
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University of Surrey
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