Researchers at Stanford University have created a sodium ion battery that offers the same amount of energy storage as lithium ion batteries but at a significantly lower cost.
The idea of a sodium ion battery is not new. However, the Stanford researchers report in Nature Energy that their approach could create a sodium ion battery with the same storage capacity as lithium ion, but at less than 80 percent of the cost.
Sodium ion battery technology could provide cost-effective energy storage at solar and wind farms.
Growing demand for battery farms
Forecasters predict that there will be a growing demand for battery farms to support the rapidly growing number of solar and wind farms.
Solar and wind farms can only capture energy when the sun shines and the wind blows. But with batteries, they can store unused captured energy and release it later, when it is dark or when there is no wind.
At present, the technology that offers the best performance for this type of storage is the lithium-ion battery. Indeed, as one of the Stanford team, chemical engineer Zhenan Bao, remarks, “Nothing may ever surpass lithium in performance.”
“But,” she adds, “lithium is so rare and costly that we need to develop high-performance but low-cost batteries based on abundant elements like sodium.”
Around a quarter of the cost of a battery is the cost of the materials. Lithium costs around $15,000 a ton once it has been mined and refined for use as electrode material. In comparison, the cost of sodium as the electrode material is around $150 a ton.
The negatively-charged partner to the positively-charged sodium ion in the battery is myo-inositol.
Myo-inositol is an abundant organic compound which can be produced from rice bran and other sources, such as from byproducts of milling corn.
In their study, the researchers focused mainly on comparing the cost-performance of their sodium ion battery to the latest lithium ion technology.
For example, they optimized the charging cycle of the battery. The charging cycle determines how efficiently a battery stores electricity coming into it and then also how efficiently it releases it when there is a demand.
Lithium ion batteries have a very high voltage and energy density, which makes them ideal for portable applications where low weight and small volume are important – such as in mobile phones, laptops, and electric vehicles.
Sodium ion batteries have a lower voltage and energy density, which would make them unsuitable for portable applications but ideal for electrical grids and power plants.
One of the things that the team plans to work on next is to look at how big their sodium ion battery would have to be in order to store the same amount of energy as a lithium ion one.