Leave it to Tesla to make something geeky like lithium-ion batteries produced with bits of silicon seem cool. But that new secret sauce, revealed by Tesla CEO Elon Musk last week, belies an important point.

For over a year, a little known startup, Amprius, has been selling its own version for cell phones, tablets and drones. Backed by Silicon Valley investors, like Google executive chairman Eric Schmidt, the company is hoping to perfect an innovative idea that could make batteries last significantly longer.

Researchers and battery giants have spent decades working on adding silicon to lithium-ion batteries to increase the energy they can store. Eventually, most people in the industry think it will become standard.

But making the silicon work is a difficult challenge because it swells and can crack the battery. Despite all the attention, manufacturers have been slow to bring these batteries to market.