A Better Battery for Laptops

Boston-Power ramps up production of its long-lasting battery.

Staying power: These battery cells are capable of recharging up to 80 percent of their capacity in 30 minutes, and they retain 80 percent of their strength after three years. The image on bottom shows a side-by-side comparison of the heat given off by two batteries generating the same level of energy: on the left is a battery from a current market leader, and on the right, Boston-Power’s Sonata battery. The green colors represent cooler temperatures. High temperatures can lead to explosive battery malfunction. (The brightly colored section outlined in black represents the batteries. The remaining area shows heat emitted by the laptop.) Credit: Boston-Power

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.

The company has also made the battery safer by separating several conventional safety measures and by inventing new ones. In existing notebook batteries, the current interrupt device and the thermal fuse are packaged on top of each other in the cell's lid. But by separating these elements from each other, the company has built an extra layer of redundancy into the system. These elements are able to control and cut off the current flow, should the battery begin to overcharge. The company has also devised a new ventilation system to alleviate the pressure and heat before they build to catastrophic levels. With aluminum in its canister, rather than carbon steel or nickel, as is common, the Sonata's shell softens much sooner at high temperatures and then self-destructs with a hiss. More-durable elements like carbon steel, which melts at even higher temperatures than aluminum, exacerbate explosions by letting extraordinary pressure and heat build inside the cell until its breaking point. (This is why conventional laptops emit loud booming cracks when they burn.)

"There is a lot of progress being made in battery technology with different chemistries," says Robert Kanode, president and CEO of Valence Technology, an Austin, TX, startup that manufactures phosphate lithium-ion batteries. His company is a competitor with Boston-Power, but Kanode adds, "We know we will not be standing alone: this will be a huge market with many viable players in it."

Lampe-Onnerud says that Boston-Power is in discussions with most of the world's top-tier notebook makers, including Hewlett-Packard, which over the past two years has worked closely with the company, helping it design battery packs that can be dropped into existing notebooks.

"The Sonata opens up a whole new business model for notebook manufacturers that hasn't been available in the past," says Ifty Ahmed, a general partner with Oak Investment Partners, who worked on the deal. Although notebook makers can presently offer a three-year warranty for a computer, they can't make the same offer on a battery, a component that can cost about 10 percent of a laptop's total value. "The market for warranties is extremely profitable," Ahmed says. "So if you can sell a warranty on the battery for three years, you have a very exciting idea."

Boston-Power says that it is focused on commercializing the Sonata, but it also believes that its patented safety features could eventually be used in lithium-ion batteries for smaller consumer-electronics devices as well as for hybrid electric vehicles.

http://www.technologyreview.com/Energy/20015/