Researchers Spin Seaweed Into the Perfect Separator Material for High-Performance Sodium Batteries

Researchers at the University of Bristol, Imperial College, and University College London have put together a technique for using a material derived from seaweed as a separator in batteries — creating a path to more environmentally-friendly energy storage with increased efficiency over current technologies.

"The aim of a separator is to separate the functioning parts of a battery — the plus and the minus ends — and allow free transport of the charge," explains Jing Wang, first author and student at the Bristol Composites Institute (BCI), of the work. "We have shown that seaweed-based materials can make the separator very strong and prevent it being punctured by metal structures made from sodium. It also allows for greater storage capacity and efficiency, increasing the lifetime of the batteries — something which is key to powering devices such as mobile phones for much longer."

Designed for use in sodium metal batteries, which are being investigated as a future replacement for lithium-based batteries, the separator material is created from a material derived from natural brown seaweed and made suitable for use in the batteries through electrospinning into nanofibers. Despite its natural origins and the lack of additives, the team found it offered stable and long-term charge-discharge cycling under high current densities — key to the hopes of replacing less environmentally-friendly alternatives.

"I was delighted to see that these nanomaterials are able to strengthen the separator materials and enhance our capability to move towards sodium-based batteries," adds Steve Eichhorn, research lead and professor at the BCI. "This means we wouldn’t have to rely on scarce materials such as lithium, which is often mined unethically and uses a great deal of natural resources, such as water, to extract it. This work really demonstrates that greener forms of energy storage are possible, without being destructive to the environment in their production."

"This approach provides a new perspective and design guideline to stabilize other metallic batteries such as potassium-, zinc-, aluminum-, calcium-, and magnesium-metal based systems," the researchers conclude, "exhibiting a promising solution for enhancing their cyclability combined with the optimized electrolyte systems.

"Considering the renewability of the precursor and the scalability at relatively low cost in this environmentally-benign synthesis process, this work offers new opportunities for realizing low-cost, sustainable, safe-credible, and high-energy-density rechargeable Na-metal batteries in large-scale energy storage in the near future."

The team's work has been accepted for publication in the journal Advanced Materials, with an open-access preprint available on the Wiley Online Library.