Tag Archives: Hongjie Dai

Stanford team adds new energy (with graphene and carbon nanotubes) to 100 year old battery design

A nickel-iron battery designed to be recharged 100 years ago by Thomas Edison for use in electric vehicles has been revived with the addition of graphene. From the June 26, 2012 news item by Mark Schwartz on EurekAlert,

Designed in the early 1900s to power electric vehicles, the Edison battery largely went out of favor in the mid-1970s. Today only a handful of companies manufacture nickel-iron batteries, primarily to store surplus electricity from solar panels and wind turbines.

“The Edison battery is very durable, but it has a number of drawbacks,” said Hongjie Dai, a professor of chemistry at Stanford. “A typical battery can take hours to charge, and the rate of discharge is also very slow.”

Now, Dai and his Stanford colleagues have dramatically improved the performance of this century-old technology. The Stanford team has created an ultrafast nickel-iron battery that can be fully charged in about 2 minutes and discharged in less than 30 seconds. The results are published in the June 26 [2012] issue of the journal Nature Communications.

Here’s how the battery worked originally and what they’ve done to improve it,

Edison, an early advocate of all-electric vehicles, began marketing the nickel-iron battery around 1900. It was used in electric cars until about 1920. The battery’s long life and reliability made it a popular backup power source for railroads, mines and other industries until the mid-20th century.

Edison created the nickel-iron battery as an inexpensive alternative to corrosive lead-acid batteries. Its basic design consists of two electrodes – a cathode made of nickel and an anode made of iron – bathed in an alkaline solution. “Importantly, both nickel and iron are abundant elements on Earth and relatively nontoxic,” Dai noted.

Carbon has long been used to enhance electrical conductivity in electrodes. To improve the Edison battery’s performance, the Stanford team used graphene – nanosized sheets of carbon that are only one-atom thick – and multi-walled carbon nanotubes, each consisting of about 10 concentric graphene sheets rolled together.

“In conventional electrodes, people randomly mix iron and nickel materials with conductive carbon,” Wang explained. “Instead, we grew nanocrystals of iron oxide onto graphene, and nanocrystals of nickel hydroxide onto carbon nanotubes.”

This technique produced strong chemical bonding between the metal particles and the carbon nanomaterials, which had a dramatic effect on performance. “Coupling the nickel and iron particles to the carbon substrate allows electrical charges to move quickly between the electrodes and the outside circuit,” Dai said. “The result is an ultrafast version of the nickel-iron battery that’s capable of charging and discharging in seconds.”

The Stanford researchers created a 1-volt ‘graphene-enhanced’ nickel-iron prototype battery for experimentation in the lab. This battery can power a flashlight but the researchers are hoping to scale up so that the battery could be used for the electrical grid or transportation.

The lead author for the study is Hailiang Wang, a Stanford graduate student. Other co-authors of the study are postdoctoral scholars Yongye Liang and Yanguang Li, graduate student Ming Gong, and undergraduates Wesley Chang and Tyler Mefford also of Stanford; Jigang Zhou, Jian Wang and Tom Regier of Canadian Light Source, Inc.; and Fei Wei of Tsinghua University.

ETA: June 27, 2012: Here, by the way, is an electric vehicle powered by Edison’s battery circa 1910, downloaded from the Stanford University site (http://news.stanford.edu/news/2012/june/ultrafast-edison-battery-062612.html) and courtesy of the US National Park  Service.

To demonstrate the reliability of the Edison nickel-iron battery, drivers rode a battery-powered Bailey in a 1,000-mile endurance run in 1910. Courtesy: US National Park Service

Get the platinum out

They’ve been using platinum catalysts, in fuel cells and metal-air batteries, which over the last five years has ranged in cost from just under $800/oz to over $2200/oz. My March 13, 2012 posting about fuel cells noted that the use of expensive metals that are not very efficient catalysts was holding back their development and entry into the marketplace,

Advances in fuel-cell technology have been stymied by the inadequacy of metals studied as catalysts. The drawback to platinum, other than cost, is that it absorbs carbon monoxide in reactions involving fuel cells powered by organic materials like formic acid. A more recently tested metal, palladium, breaks down over time.

Now chemists at Brown University have created a triple-headed metallic nanoparticle that they say outperforms and outlasts all others at the anode end in formic-acid fuel-cell reactions.

Another group of researchers at Stanford University and other institutions is suggesting an alternative to a platinum catalyst, a multi-walled carbon nanotube. From the May 27, 2012 news release written by Mark Shwartz on EurekAlert,

Multi-walled carbon nanotubes riddled with defects and impurities on the outside could replace some of the expensive platinum catalysts used in fuel cells and metal-air batteries, according to scientists at Stanford University. Their findings are published in the May 27 online edition of the journal Nature Nanotechnology.

“Platinum is very expensive and thus impractical for large-scale commercialization,” said Hongjie Dai, a professor of chemistry at Stanford and co-author of the study. “Developing a low-cost alternative has been a major research goal for several decades.”

For the study, the Stanford team used multi-walled carbon nanotubes consisting of two or three concentric tubes nested together. The scientists showed that shredding the outer wall, while leaving the inner walls intact, enhances catalytic activity in nanotubes, yet does not interfere with their ability to conduct electricity.

“A typical carbon nanotube has few defects,” said Yanguang Li, a postdoctoral fellow at Stanford and lead author of the study. “But defects are actually important to promote the formation of catalytic sites and to render the nanotube very active for catalytic reactions.”

Here’s how it works, from the May 27, 2012 news release on EurekAlert,

For the study, Li and his co-workers treated multi-walled nanotubes in a chemical solution. Microscopic analysis revealed that the treatment caused the outer nanotube to partially unzip and form nanosized graphene pieces that clung to the inner nanotube, which remained mostly intact.

“We found that adding a few iron and nitrogen impurities made the outer wall very active for catalytic reactions,” Dai said. “But the inside maintained its integrity, providing a path for electrons to move around. You want the outside to be very active, but you still want to have good electrical conductivity. If you used a single-wall carbon nanotube you wouldn’t have this advantage, because the damage on the wall would degrade the electrical property.”

These are two different perspectives on the reason for why fuel cells and other batteries have not had the expected impact on the marketplace. The team at Brown University states the problem as an issue with the effectiveness of the metal catalysts where the Stanford-led team states the problem as being the cost of the metal used. Dexter Johnson in a March 9, 2012 posting on the Nanoclast blog on the IEEE (Institute of Electrical and Electronics Engineers) website suggested a third issue,

One of the fundamental problems with fuel cells has been the cost of producing hydrogen. While hydrogen is, of course, the most abundant element, it attaches itself to other elements like nitrogen or fluorine, and perhaps most ubiquitously to oxygen to create the water molecule. The process used to separate hydrogen out into hydrogen gas for powering fuel cells now relies on electricity produced from fossil fuels, negating some of the potential environmental benefits.

In his May 30, 2012 posting about this new work from Stanford, Dexter notes yet another issue impeding widespread commercialization,

… but the two main issues that have prevented fuel cells from gaining wider adoption—at least in the area of powering automobiles—are the costs of isolating hydrogen and building an infrastructure that would deliver that hydrogen to the automobiles.

Dexter mentions another application (metal-air batteries) that may benefit more from this latest work (from Dexter’s May 30, 2012 posting),

I think it’s all together possible that researchers at IBM and the US national labs who have been working on metal-air batteries for years now might be somewhat more interested in this line of research than fuel-cell manufacturers.

As one of the researchers notes (from the May 27, 2012 news release on EurekAlert),

“Lithium-air batteries are exciting because of their ultra-high theoretical energy density, which is more than 10 times higher than today’s best lithium ion technology,” Dai said. “But one of the stumbling blocks to development has been the lack of a high-performance, low-cost catalyst. Carbon nanotubes could be an excellent alternative to the platinum, palladium and other precious-metal catalysts now in use.”

The Stanford team made one other discovery as they were testing the carbon nanotubes,

The Stanford study might also have resolved a long-standing scientific controversy about the chemical structure of catalytic active sites where oxygen reactions occur. “One group of scientists believes that iron impurities are bonded to nitrogen at the active site,” Li said. “Another group believes that iron contributes virtually nothing, except to promote active sites made entirely of nitrogen.”

To address the controversy, the Stanford team enlisted scientists at Oak Ridge National Laboratory to conduct atomic-scale imaging and spectroscopy analysis of the nanotubes. The results showed clear, visual evidence of iron and nitrogen atoms in close proximity.

“For the first time, we were able to image individual atoms on this kind of catalyst,” Dai said. “All of the images showed iron and nitrogen close together, suggesting that the two elements are bonded. This kind of imaging is possible, because the graphene pieces are just one-atom thick.”

Dai noted that the iron impurities, which enhanced catalytic activity, actually came from metal seeds that were used to make the nanotubes and were not intentionally added by the scientists. The discovery of these accidental yet invaluable bits of iron offered the researchers an important lesson. “We learned that metal impurities in nanotubes must not be ignored,” Dai said.