Among the many technologies being developed in the field of batteries are those that try to combine the advantages of sodium-ion batteries with those of solid electrolyte. Indeed, sodium ion batteries are considered attractive because, compared to lithium ion batteries, they make use of more common and easily available resources and are also less expensive.

Solid-state batteries are safer and allow both higher energy density and faster recharging. The best of both worlds, in short. But things are easier said than done. There are in fact problems in production that make it difficult to raise volumes to acceptable levels to meet mass market demands.

10 times higher conductivity

A study conducted by Osaka professors Atsushi Sakuda and Akitoshi Hayashi, both from Osaka University's Faculty of Engineering, has circumvented this limitation and found a way to produce sulphides containing sodium in large quantities.

The team of Japanese researchers who took part in the project discovered that, by using sodium polysulphides (i.e. sulphides with two or more sulphur atoms), a solid sulphide electrolyte can be made that has very high conductivity. The highest among the electrolytes used so far on sodium ion batteries. It is even 10 times higher than required.

The production of polysulphides for sodium ion batteries with solid electrolyte

A process that is good for all sodium sulphides

"This newly developed process is useful for the production of almost all sodium sulphur materials, including solid electrolytes and active electrode materials," said Professor Sakuda.

'Furthermore,' he added, 'compared to conventional methods, this process makes it easier to obtain materials that exhibit higher performance, so we believe it will become a mainstream process for the future development of all-solid-state sodium battery materials.

Indeed, as explained in the article published in the scientific journals Energy Storage Materials and Inorganic Chemistry, the mass synthesis of electrolytes with this conductivity is crucial for the real use of all-solid-state sodium batteries.