The new battery uses iron oxide crystals on graphene sheets and nickel hydroxide crystals on multi-walled carbon nanotubes to charge and discharge so quickly. (Photo : Hialiang Wang, Stanford Univer)
A technology invented more than a century ago by Thomas Edison has gotten its second wind thanks to a team of Stanford University scientists. They have successfully improved upon Edison's rechargeable nickel-iron battery, which could be used to help power electric vehicles and have other uses thanks to its fast charge times.
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The nickel-iron battery was developed by Edison back in 1901 as a power source for electric vehicles. Edison himself claimed that the nickel and iron design was "far superior to batteries using lead plates and acid."
"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."
Today the nickel-iron batteries have largely fallen out of use thanks to their low energy retention and high cost of manufacturing. Nickel-iron batteries, however, are incredibly useful in storing charge since they can tolerate abuse well and can last as much as 20 years. Because of that, they are popular with solar grids and other electrical grids to store surplus charge.
The scientists from Stanford have found a way to charge the nickel-iron battery and discharge it incredibly fast. Their battery can be fully charged in around 2-and-a-half minutes, and discharged in 30 seconds.
"We have increased the charging and discharging rate by nearly 1,000 times," said Hailiang Wang, lead author of the study. "We've made it really fast."
The team accomplished this by improving on the electrodes.
"In conventional electrodes, people randomly mix iron and nickel materials with conductive carbon," Wang said. "Instead, we grew nanocrystals of iron oxide onto graphene, and nanocrystals of nickel hydroxide onto carbon nanotubes."
The applications could be taken further than Edison's original intention of creating a power source for vehicles.
For instance, with such fast charge and discharge times, the nickel-iron battery would be incredibly useful in the field for the military or a team of researchers.
The only major drawback, the team admits, is the amount of charge decay.
"It doesn't have the charge-discharge cycling stability that we would like," Dai said. "Right now it decays by about 20 percent over 800 cycles. That's about the same as a lithium-ion battery. But our battery is really fast, so we'd be using it more often. Ideally, we don't want it to decay at all.