Battery startup Amprius says it has developed batteries capable of storing twice as much energy as anything on the market today, thanks to nanostructured silicon electrodes. The company says it is partnering with several as-yet unnamed major consumer electronics manufacturers to bring the batteries to market by early 2012. The batteries will allow portable electronics to run 40 percent longer without a recharge.

Amprius also says it is working with several major automakers who are evaluating the electrode materials for use in batteries for electric vehicles. The company is not yet disclosing these commercial partners, either.

When a lithium-ion battery is charged, lithium ions move from its cathode to its anode, while electrons flow in through an external electrical circuit. The process is reversed during discharge. The more lithium the anode can take in, the more total energy the battery can store, and the longer it can last. For the past 30 years, lithium-ion batteries have used carbon anodes. With no new materials, the total energy storage of these batteries has improved by only about 7 percent every year due to incremental engineering refinements.

Silicon has 10 times the theoretical lithium storage capacity of the carbon used to make battery anodes, but it's been difficult for researchers to make it into a practical battery electrode. As large volumes of lithium ions move in and out of the material during charge and discharge, silicon swells and cracks.

In 2007, Yi Cui, a Stanford University materials science and engineering professor, demonstrated that nanostructured silicon films could be charged and discharged of lithium without experiencing these mechanical problems, making a potential anode material that could as much as double the energy storage of lithium batteries.