Cheap sodium-sulfur battery boasts 4x the capacity of lithium-ion

An international team of scientists eyeing next-generation energy storage solutions have demonstrated an eco-friendly and low-cost battery with some exciting potential. The group’s novel sodium-sulfur battery design offers a fourfold increase on energy capacity compared to a typical lithium-ion battery, and shapes as a promising technology for future grid-scale energy storage.

The team’s creation falls into a category of batteries known as molten-salt batteries, which have been around in various forms for around 50 years. As the emphasis on renewable energy continues to grow, scientists are bullish on the potential of molten-salt batteries to store it, owing to their relative affordability and reliance on commonly available materials.

This could, theoretically, see them built on the larger scales needed to store vast amounts of renewable energy. Typical versions of these rely on a sodium-sulfur chemistry and hold their electrodes at high temperatures to keep the electrolyte in a liquid molten state. Scientists in China and Australia have teamed up to develop their own version, which they say offers greatly improved performance at room temperature instead.

“When the sun isn’t shining and the breeze isn’t blowing, we need high-quality storage solutions that don’t cost the Earth and are easily accessible on a local or regional level,” said lead researcher Dr Shenlong Zhao from the University of Sydney. “We hope that by providing a technology that reduces costs we can sooner reach a clean energy horizon."

Zhao and his colleagues set out to address a couple of shortcomings with current sodium-sulfur batteries, relating to their short life cycles and limited capacities, which has hindered their practicality in commercial applications. The team’s design makes use of carbon-based electrodes and a thermal degradation process known as pyrolysis to alter the reactions between the sulfur and sodium.

The result is a sodium-sulfur battery with a high capacity of 1,017 mAh g−1 at room temperature, which the team notes is around four times that of a lithium-ion battery. Importantly, the battery demonstrated good stability and retained around half of this capacity after 1,000 cycles, described in the team’s paper as “unprecedented.”

“Our sodium battery has the potential to dramatically reduce costs while providing four times as much storage capacity,” said Dr Zhao. “This is a significant breakthrough for renewable energy development which, although reduces costs in the long term, has had several financial barriers to entry.”

Having demonstrated the technology in coin cell batteries in laboratory testing, the researchers are now working on pouch cell versions as they eye a path to commercial use.

“It probably goes without saying but the faster we can decarbonize – the better chances we have of capping warming,” said Zhao. “Storage solutions that are manufactured using plentiful resources like sodium – which can be processed from sea water – also have the potential to guarantee greater energy security more broadly and allow more countries to join the shift towards decarbonization.”

The research was published in the journal Advanced Materials. 

Source: University of Sydney