Energy utilities are increasingly looking for batteries that can help stabilize the grid. By quickly storing and delivering charge, batteries could accommodate fluctuations in supply and demand, and help to incorporate variable sources of power such as wind and solar. However, currently available battery technologies are either too expensive or don't last for enough charge cycles to be practical.
Researchers at Stanford University have now demonstrated a high-efficiency new nanomaterial battery electrode that lasts for 40,000 charge cycles without significantly losing its charge-holding capacity. The work was led by Yi Cui, a materials science and engineering professor at Stanford University. Cui says the electrode is a first step toward a new type of low-cost battery suitable for storing large amounts of electricity within the power grid.
Cui's new battery chemistry uses inexpensive, abundant materials. It relies on the same principle employed in lithium-ion batteries—moving sodium or potassium ions between electrodes during charging and discharging—but does it much more cheaply. "For grid storage, the battery can be huge, and using sodium and potassium is very attractive because they are so abundant and cheap," Cui says. These batteries will use water-based electrolytes that are cheaper and easier to use than organic solvent-based electrolytes used in lithium-ion batteries.
The new electrodes, demonstrated in a paper posted online today in the journal Nature Communications, are also based on commonly available materials. The researchers start with the pigment Prussian Blue, an iron and cyanide compound. They replace half the iron with copper, and make crystalline nanoparticles of the resulting compound, which they coat on a cloth-like carbon substrate. Then they immerse this electrode in a potassium nitrate electrolyte solution.