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A new sodium-based battery can store the same amount of energy as a state-of-the-art lithium ion at a substantially lower cost.
As a warming world moves from fossil fuels toward renewable solar and wind energy, industrial forecasts predict an insatiable need for battery farms to store power and provide electricity.
Chemical engineer Zhenan Bao and materials scientists Yi Cui and William Chueh of Stanford University aren’t the first researchers to design a sodium ion battery. But they believe their approach has the price and performance characteristics to create a sodium ion battery that costs less than 80 percent of a lithium ion battery with the same storage capacity.
“Nothing may ever surpass lithium in performance,” Bao says. “But lithium is so rare and costly that we need to develop high-performance but low-cost batteries based on abundant elements like sodium.”
With materials constituting about one-quarter of a battery’s price, the cost of lithium—about $15,000 a ton to mine and refine—looms large. Researchers say that’s why they are basing the new battery on widely available sodium-based electrode material that costs just $150 a ton.
The sodium-based electrode has a chemical makeup common to all salts: It has a positively charged ion—sodium—joined to a negatively charged ion. In table salt, chloride is the positive partner, but in the battery a sodium ion binds to a compound known as myo-inositol.
Unlike the chloride in table salt, myo-inositol isn’t a household word—but it is a household product, found in baby formula and derived from rice bran or from a liquid byproduct of the process used to mill corn. Crucial to the idea of lowering the cost of battery materials, myo-inositol is an abundant organic compound familiar to industry.
The sodium salt makes up the cathode, the pole of the battery that stores electrons. The battery’s internal chemistry shuttles those electrons toward the anode, which in this case is made up of phosphorous. The more efficiently the cathode shuttles those electrons toward and backward versus the anode, the better the battery works.