Boston-Power says that it's poised to enter the market for portable power, with a notebook battery the company claims is safer, lasts longer, and can be charged faster. The Westborough, MA, startup recently announced that it is more than tripling production of its high-performance battery, called the Sonata, after receiving $45 million in a third round of venture financing. The move puts the company in a position to mass-produce and commercialize its next-generation lithium-ion battery within months.

"In partnership with GP Batteries, one of Asia's largest battery manufacturers, we now have our second factory up and running in the greater China region," says Christina Lampe-Onnerud, the company's founder and CEO. In 2002, Technology Review named Lampe-Onnerud one of its top innovators under the age of 35 for her efforts to develop better-performing lithium-ion batteries with less volatile substances. Based on that research, she founded Boston-Power in 2005. Now, after raising $68 million in total, she says that her company will be able to manufacture a million battery cells per month by the end of 2008.

Oak Investment Partners, based in Westport, CT, provided this latest infusion of capital, building upon earlier investments by Venrock Associates, Granite Global Ventures, and Gabriel Venture Partners.

Although the Sonata will not offer greater energy capacity per use--with a four-hour run time, its performance will be average for the market--the company hopes that the battery's three-year life span, innovative safeguards, and ability to recharge quickly will help it gain a foothold in the battery market. As opposed to existing notebook batteries, which can take an hour to recharge to 80 percent capacity, the Sonata can reach that same level in just 30 minutes, according to Boston-Power. And whereas current batteries degrade very quickly, permanently losing up to 50 percent of their capacity within months, the Sonata retains up to 80 percent of its capacity over three years. In fact, since the typical laptop battery tends to degrade very rapidly, the Sonata will have a greater per-use capacity in the long run.

To make the cell retain its capacity over its lifetime, Boston-Power found it necessary to change the current lithium-ion design. The company identified a combination of new chemistry mixtures and electrode compositions, and it created a new shape--all of which enables a consistent performance over the cell's lifetime. The different shape made it possible for the company to increase the volume of the cell and more efficiently use the space within a battery pack, allowing it to reach energy-storage levels competitive with current conventional batteries.

In the past, it has been very difficult to make lithium-ion cells larger, since a larger energy density creates a potential for greater catastrophic malfunctioning. Conventional lithium-ion batteries use cobalt oxides, but the substance has been partly responsible for some of the more dramatic laptop explosions in recent years. So instead of using cobalt, which also tends to degrade quickly, the company incorporated manganese. Boston-Power isn't the only company using manganese; other companies, such as Compact Power, are also trying to take advantage of its stability. Boston-Power is incorporating the element into a larger than average cell.