The idea for using sodium in batteries dates back to the 1980s. At the time, lithium was preferred to sodium as the material of choice and it has been widely used ever since for portable electronic devices such as tablets, laptops and electric vehicles. However, lithium is rare and therefore, more expensive than sodium. The RS2E researchers therefore turned towards sodium, a thousand times more abundant. They developed Na-ion battery prototypes where sodium ions move from one electrode to another in a liquid during the charge and discharge cycles.
The team was able to develop the first sodium-ion prototype in the "18650" format, a cylindrical 1.8cm diameter, 6.5cm in height - which should facilitate technology transfer to existing production units.
The energy density of the prototype batteries amounts to 90Wh/kg, a figure already comparable with the first Li-ion batteries. The maximum number of charge/discharge cycles that a battery can withstand without any significant loss of performance-exceeds 2000 cycles.
The next stage of the project is to optimise and increase the reliability of processes with a view to future commercialisation.
