Lithium-ion batteries pack extra power, challenges

The prospect of flying in a so-called plastic airplane was already unnerving for some.

Now there’s the added concern of Boeing’s 787 Dreamliner using the same kind of batteries that used to overheat and ignite laptops made by Dell, Hewlett-Packard, Apple and others. Battery mishaps led to the plane’s grounding this week by U.S. and European regulators.

Lithium-ion batteries are state of the art, producing the most energy in the lightest package at an acceptable price.

But they have had problems and continue to challenge engineers to manage the temperature generated in their chemical reactions, particularly as larger versions are produced for vehicles and now airplanes.

“It’s clear that there are some issues associated with thermal management,” said Donald Sadoway, a battery expert and the John F. Elliott Professor of Materials Chemistry at the Massachusetts Institute of Technology.

Since Sony began manufacturing them in 1990, lithium-ion batteries have led to a revolution in consumer electronics. They allow companies to build lightweight phones, cameras, power tools and other gadgets that run a day or more on a single charge.

In a phone, the batteries are thin and the heat is dissipated by the front and back of the case, which act like cooling fins, said Sadoway.

It’s a different story when you’re talking about batteries that are nearly twice the size of a car battery, like those used in the 787.

Tesla roadsters addressed the issue by using thousands of small, finger-sized batteries, clustered together. Now larger batteries are being used in cars such as Toyota’s plug-in Prius.

Boeing is the first company to use lithium-ion technology for the main batteries in a commercial airplane. The supplier of those recently also won a contract to upgrade the International Space Station to lithium-ion batteries.

Safety remains a concern, though, especially if manufacturers try to cut costs.

Sony learned this the hard way in 2006. Errant metal flakes inside some laptop batteries it produced caused them to short-circuit, leading to sudden and sometimes spectacular fires. This resulted in recalls of more than 7 million batteries around the world, affecting major computer companies using Sony batteries.

“That’s a concern this industry has: You’re building a very energetic device; you’d better do it well or you’re going to have problems,” said Vince Battaglia, a specialist in battery design at the Lawrence Berkeley National Laboratory in California.

So how do the batteries work? Here’s how he would explain it to a lay person:

“It consists of two electrodes that each accept lithium. But one does it more easily than another. You get a voltage difference because of that relationship. You can use that energy and control it by discharging the battery at whatever (level) you want.”

The breakthrough with lithium-ion batteries was in the electrolyte material. Up until 1990, batteries were water-based. Researchers at Berkeley found that using an organic electrolyte led to dramatic increases in energy density, or the amount of energy in the package.

Lithium-ion batteries such as those used on the 787 have safeguards, such as controllers that trigger a shut-off if temperatures rise too much; vent built-up pressure; and prevent the batteries from bursting into flame.

A Boeing executive said the 787 has a redundant safety system with four controllers on the batteries, although that’s apparently not enough to prevent incidents and satisfy regulators.

Research continues into improving lithium-ion batteries, but the technology is now mature, said Jonathan Posner, associate professor of mechanical engineering at the University of Washington, who called the technology “a logical choice” for the 787.

“I don’t think Boeing would have used it if it wasn’t mature,” he said.

Posner said Boeing seems to have “an engineering issue that just has to be resolved. But I would be surprised if they don’t continue to use lithium-ion batteries in the 787.”

Different materials can be used in these batteries, some safer than others. Based on information posted on its website, Boeing supplier GS Yuasa appears to be using lithium cobalt oxide cathode material, which is the original material used by Sony.

“From a safety point of view, that’s not the best,” said Ji-Guang Zhang, a researcher at the Pacific Northwest National Laboratory in Richland. He said cobalt oxide batteries ignite at lower temperature than lithium batteries made with other materials, such as iron phosphate.

Supplier GS Yuasa declined to discuss whether the batteries in question use cobalt oxide and referred questions to its partner Thales Group, which didn’t promptly respond.

Still, it’s all relative.

“Theoretically, it is safe,” Zhang said. “I think it is not less safe than a gasoline-powered engine. Gas is much easier to burn than batteries.”

Battaglia said iron phosphate “has been known to sort of be safer.” But he added that “nothing is safe – you’ve still got a lot of energy and an electrolyte in there that’s flammable.”

So should people feel comfortable flying in a plane with these batteries?

“Everybody in there has a lithium cobalt oxide in their pocket, so it’s sort of a matter of scale or engineering,” Battaglia said.

One option for Boeing could be to revert to an older, safer type of battery, but it would be heavier. While nickel-metal hydride batteries – the type used in the Prius hybrid – would weigh about 50 percent more, they’d add a relatively small amount of weight to the overall airplane, Sadoway said.

“It’s not as though we’re talking about making the plane incapable of getting off the ground,” he said.