Bill Gates invests in energy storage startup Aquion

Aquion grew out of technology developed by company founder Jay Whitacre, a professor of materials science and engineering at Carnegie Mellon University. His goal was to find basic, abundant and benign materials to make cheap, modular batteries that could be used to store energy and help bring more renewable energy onto the power grid.

Whitacre's battery couples a carbon anode with a sodium-based (manganese oxide) cathode. Whitacre explained in 2011 to SmartPlanet that he used cheap materials like carbon, manganese, water and various kinds of cheap plastics to keep costs low. He even found way to reconfigure carbon, so it can be taken from corn syrup or other forms of carbon.  He also focused on benign materials. Unlike other batteries that use solvent-based electrolytes, Whitacre's version uses water-based electrolytes to move ions between the electrodes when charging and discharging.

He spent two years before figuring out the ideal chemistry for non-toxic batteries. By 2009, Whitacre had spun his tech into startup 44 Tech—a name that would change the following year to Aquion Energy.