No. 361: Use water solution in place of organic solvent as electrolyte for a secondary sodium-ion battery (November 25, 2011)

A research team of Kyushu University led by an associate professor Shigeto Okada successfully built a sodium-ion secondary battery that uses water solution in place of organic solvent as electrolyte on trial. The trial product is the beaker cell type, and it has a capacity of about one fifth of the existing lithium-ion secondary battery. The research team will work on the trial product to make it a coil-cell type battery, and try to increase the capacity to about 75% of the existing lithium-ion secondary battery.

The sodium-ion secondary battery is very promising as an inexpensive next-generation secondary battery, but ongoing research projects mostly use organic solvent as electrolyte. This is because an appropriate negative-electrode material is not developed for a sodium-ion secondary battery that uses water solution as electrolyte. The research team verified that a material made of sodium and titanium can be used as negative-electrode. The trial product uses a material made of sodium, manganese, and oxygen as positive-electrode and water solution of sodium sulfate can charge and discharge at room temperature. If the trial product is put into practical application, the cost of sodium-ion battery will be one fourth of the existing lithium-ion battery.