Graphene gives Thomas Edison's battery a new life
A rechargeable battery technology developed by Thomas Edison more than a century ago has been upgraded by Stanford University researchers.
The original nickel-iron battery was made at the beginning of the 20th Century to power electric cars.
But today, only a few companies use it, mainly to store surplus electricity from solar panels and wind turbines.
The original Edison battery takes hours to charge, but the improved version charges in minutes.
The research appears in the journal Nature Communications.
The original battery consists of a cathode made of nickel and an anode made of iron, bathed in an alkaline solution.
Carbon is usually used as the conductive element - but to improve its performance, the Stanford team used graphene, a sheet of carbon just one atom thick.
"In conventional electrodes, people randomly mix iron and nickel materials with conductive carbon," said Stanford postgraduate student Hailiang Wang, lead author of the study.
"Instead, we grew nanocrystals of iron oxide onto graphene, and nanocrystals of nickel hydroxide onto carbon nanotubes."
This method helped the scientists increase the charging rate of the battery by nearly 1,000 times, he added.
The prototype battery is only powerful enough to operate an electric torch, but the team hopes that one day it will be used to power modern electric vehicles - or at least as a "power boost" source.
"Hopefully we can give the nickel-iron battery a new life," said Hongjie Dai, a professor of chemistry at Stanford.
Mr Wang said their battery could complement the lithium-ion batteries currently used in many electric vehicles, giving them "a real power boost for faster acceleration and regenerative braking".
It could also be used in emergency situations, when something needs to be charged very quickly.
Electric cars are not a new concept, the first one appeared in the 19th Century.
Many of the ones made in the early 1900s were powered by the Edison battery, which was also used as back-up power source for railways and the mining industry.