More Bang for Your Battery

New nanotechnology launches longer lasting batteries.

By Kathleen Kocks

Jessica McConnell

Is the world becomes increasingly populated with mobile electronic products, one of the most ubiquitous pieces of equipment is the battery. From the watch on your wrist to satellites in space, batteries are the enablers of the technology, powering an array of products used in a wide range of applications.

While its design and performance have evolved since Italian Count Alessandro Volta invented the battery in 1799, there’s plenty of room for further improvement. Battery life, power, recharging times, size, and weight are just a few parameters that beg for upgrades. In fact, drawbacks in current battery technology are impeding advancements in existing products—including cell phones and laptop computers—and in new applications—such as the electric car.

This is why GW Professor Michael J. Wagner and his team at the Wagner Lab within the University’s Columbian College of Arts and Sciences Department of Chemistry are leading a charge to improve the battery.

An associate professor of chemistry, Wagner defines himself as a scientist and nanoresearcher. He works in the world of nanotechnology, which uses materials designed at the atomic level (dubbed “nanomaterials”) to improve existing technology, as well as create new technology. It is a scientific field with explosive potential to change the world much as semiconductors did. Nanotechnology is at the heart of Wagner’s battery research.

“We began this research about five years ago, and the simplest way to explain it is to say we are trying to find better materials to make better batteries and improve their performance,” Wagner explains.

“There are various measures that define battery performance. One is energy density, which is a measure of how much energy a battery can store. Another is storage life, which relates to how long a battery remains charged. Another area is how fast you can recharge a battery. And there is cycle life, which relates to how many times you can recharge a battery before it won’t recharge and has reached the end of its service life.”

Introduced to the commercial market in 1991, lithium ion (Li-ion) rechargeable batteries are among the three most prevalent types of rechargeable batteries used in electronics today. The other two types—nickel-cadmium (NiCad) and nickel-metal hydride (NiMH)—are being or have been replaced by Li-ion batteries in most applications.

Li-ion batteries work pretty much as any other battery does. They contain lithium ions swimming in an electrolyte composed of lithium salts and an organic solvent. The ions shuffle between two electrodes: one of graphite (the negative electrode) and the other of metal oxide (the positive electrode). As the battery is charged, the ions are attracted to the graphite; during discharging, the ions head for the metal oxide. Connecting a wire between the electrodes creates a circuit that powers whatever is added to the circuit.

Michael J. Wagner’s research on batteries and a relatively new type of nanomaterial called fullerenes has resulted in longer lasting batteries.

Jessica McConnell

In comparison to NiCad and NiMH batteries, Li-ion batteries are lighter (i.e., have a higher energy and power density); they also have a slower self-discharge rate. As for drawbacks, their life span is determined by two factors: the date of their manufacture (shelf life—they begin to age after they are manufactured, whether used or not) and how many times they are charged/discharged (cycle life). Each time the battery is charged/discharged, it loses more and more of its capacity to be charged.

“One of our successes has been to find a way to dramatically improve the cycle life of lithium ion batteries, so that very, very little capacity is lost during charge and discharge,” Wagner explains. “In other words, we managed to make the battery last longer and retain its ability to get charged and stay charged. This means that one doesn’t have to replace batteries very often.”

To accomplish this, Wagner’s team used a relatively new type of nanomaterial: fullerenes. Fullerenes are a form of carbon discovered in 1985. Like two other forms of carbon—diamonds and graphite—fullerenes have qualities that make them attractive for industrial applications. Fullerenes are large carbon cage-like molecules, the most famous being composed of 60 carbon atoms in the shape of a soccer ball, named C60 or Buckministerfullerene. Current methods of mass-producing fullerenes yield a great mixture of fullerenes, ones composed of as few as 60 to more than 500 carbons.

Incidentally, the process of obtaining pure small fullerenes is very expensive; pure C60 is more than three times as expensive as gold. Other pure small fullerenes are even more expensive; C70 is 40 times the price of gold. Yet, their industrial potential makes them marketable even at that price.

“We thought the similarities between graphite and fullerenes were very interesting,” Wagner says. “To see if we could provide a more stable graphite electrode, we coated the electrode’s surface with all kinds of fullerene materials. Then we removed various portions and discovered that the fullerenes that worked for our project were the larger fullerenes, which until our discovery had no application.

“So, we are using the waste that is generated when creating the smaller fullerenes. Not only are we improving the life of the battery, but we are improving it with inexpensive ‘garbage.’”

How much has the battery life been improved? According to testing thus far, Wagner’s team has found that graphite treated with fullerenes retains more than 99 percent of its charge capacity after 200 charge-discharge cycles, while under the same conditions, untreated graphite retains only about 21 percent of its capacity. Going forward, Wagner and his team want to better understand why the fullerenes improve the graphite’s performance. With those answers, they hope to further boost the performance and make batteries that can be charged at a very high rate—in minutes rather than hours.

Inside this inert atmosphere glove box, where no air or water is present, Wagner can safely make and test the batteries.

Jessica McConnell

Wagner’s group has applied for a patent for its Li-ion battery development. The team also is collaborating with ITT Industries and the federal government’s intelligence agencies on this research. The intelligence community is interested because many of the devices it uses are battery powered.

“Consumer electronics would certainly be a huge market for the improved battery,” Wagner says. “Another immediate application would be to replace nickel hydride batteries currently used in satellites. They are heavy but can be cycled many thousand times. Current lithium-ion batteries are very light but can’t be cycled as often. Our battery may resolve this drawback,” Wagner explains. “But if you want to talk about the ‘1,000-pound-gorilla’ market for our battery, it’s the emerging market for electric and hybrid vehicles. That’s the big one.”

As the battery research goes forward, Wagner and his team have other intriguing projects in the works.

“We are studying nanomaterials to create better flat-screen displays with better resolution and lower power needs,” he says. “Another project involves magnetic refrigeration, which cools by using magnetic nanomaterials that could replace current gas-based (i.e., Freon) cooling units in refrigerators and air conditioners. This technology may also be light enough for personal application—something the military is very interested in to keep soldiers cool in modern fighting gear.

“We are also studying nanomaterials for use in magnetic resonance imaging (MRI), as a way to improve the contrast in the images and make it easier for doctors to spot anomalies. And we are the only nanotechnology research group in the world investigating a process called alkaline reduction, which is a uniquely powerful method of making a range of nanomaterials that our group is testing for various applications.

“My research is in all kinds of nanomaterials,” Wagner concludes. “The common thread is to find nanomaterials that create or improve technologies and make the impossible possible.”

Kathleen Kocks is a freelance writer based in New Orleans.

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