Sodium-Ion Cell Goes Solid State

A solid-state electrolyte made from a sodium orthothiophosphate (Na₃PS₄) glass can power a sodium-ion battery at room temperature, report researchers from Osaka Prefecture University, in Japan (Nat. Commun., DOI: 10.1038/ncomms1843). Sodium-ion batteries hold promise as a less expensive alternative to lithium-ion batteries, but right now the technology requires high operating temperatures and involves a liquid electrolyte that may leak. Akitoshi Hayashi and colleagues envision a solid-state sodium-ion battery that works at ambient temperatures. His group prepared the electrolyte by heating a Na₃PS₄ glass to 270 ºC, then precipitating out a crystallized glass, or glass-ceramic. A solid-state cell made from the electrolyte with sodium-tin alloy and titanium disulfide electrodes worked through 10 charge cycles at room temperature. Although the cell’s capacity was only 40% of the theoretical capacity, the researchers are working to improve its performance by developing new electrode materials and modifying the structure of the electrolyte.