­Cheap Battery has Four Times the Capacity of Lithium-Ion

There has been a lot of research done on molten-salt batteries in recent times. The technology has a very high energy density and can often be cheaper to produce than other technologies. They are also less toxic than the Li-ion batteries that we often use now for energy storage. The low cost aspect of molten salt batteries usually comes from the fact that they are made from materials that are abundant and easy to extract in comparison to lithium. One downside of molten-salt technology is that the batteries are usually larger than lithium based batteries, which means that they may not be suitable for applications that are restricted to a smaller area, such as EVs. Molten salt batteries are generally used for renewables storage, but that also means that the lithium that would be used for renewables storage can now be employed in applications where it is really needed, making the lithium supply stretch further and reducing demand for the substance – at least until the new mines and extraction facilities that have been proposed come online.

The team from the University of Sydney are hoping that their new, low-cost battery will reduce the cost of transitioning to a decarbonised economy. Led by Dr Shenlong Zhao from the University’s School of Chemical and Biomolecular Engineering, the battery has been made using sodium-sulphur (Na-S) – a type of molten salt that can be processed from sea water. Sodium-sulphur batteries have existed for more than half a century. However, their widespread use has been limited by low energy capacity and short life cycles. Using a simple pyrolysis process and carbon-based electrodes to improve the reactivity of sulphur and the reversibility of reactions between sulphur and sodium, the researchers’ battery exhibited super-high capacity and ultra-long life at room temperature. The researchers say the Na-S battery is also a more energy dense and less toxic alternative to lithium-ion batteries, which are expensive to manufacture and recycle. Dr Zhao’s Na-S battery has been specifically designed to provide a high-performing solution for large renewable energy storage systems, such as electrical grids, while significantly reducing operational costs.

“Our sodium battery has the potential to dramatically reduce costs while providing four times as much storage capacity. This is a significant breakthrough for renewable energy development which, although reduces costs in the long term, has had several financial barriers to entry,” said lead researcher Dr Zhao. He continued, “Storage solutions that are manufactured using plentiful resources like sodium – which can be processed from sea water – have the potential to guarantee greater energy security more broadly and allow more countries to join the shift towards decarbonisation.”

The lab-scale coin batteries using the technology have been successfully fabricated and tested in the University of Sydney’s chemical engineering facility. The researchers now plan to improve and commercialise the recently fabricated Ah-level pouch cells.

The paper was published in Advanced Materials https://onlinelibrary.wiley.com/doi/10.1002/adma.202206828