Asphalt helps batteries charge more quickly
Lithium batteries can be made to charge 10 to 20 times faster by using asphalt, suggests US research.
Scientists at Rice University speeded up the charging time by making one component of a battery using carbon derived from the viscous liquid.
In tests, batteries made using asphalt charged to full power in minutes, said the researchers.
They also found that using asphalt stopped the formation of deposits that can shorten the life of a battery.
"The capacity of these batteries is enormous," said Prof James Tour, who heads the lab that developed the batteries.
"What is equally remarkable is that we can bring them from zero charge to full charge in five minutes, rather than the typical two hours or more needed with other batteries," he added.
To make their batteries, the Rice team used carbon derived from asphalt that was mixed with graphene nanoribbons and then coated with lithium metal.
Prof Tour said the manufacturing process behind this new approach was simpler than earlier techniques it had developed for making fast-charging batteries.
The Rice team has put prototype batteries through hundreds of cycles of charging and discharging to ensure the technology is stable.
This testing also revealed that the batteries were less likely to suffer the build-up of structures called "lithium dendrites" that can gradually spread through a device limiting its life.
Details of the research were revealed in the scientific journal ACS Nano.
The Rice group is just one of many developing faster-charging technologies.
Earlier this year, battery start-up StoreDot said it would introduce its quick-charging batteries in 2018, although some analysts were sceptical about its claims. Tesla, Qualcomm and many others are also working on ways to speed up charging.
Ben Wood from the CCS Insight consultancy expressed some doubts about the Rice research.
"We see so many of these claims and I have learned through experience to be extremely cautious about them," he said, adding that physics often got in the way of batteries being charged very swiftly.
Also, he added, because people now kept their phones for longer they might not like the idea of technologies that forced them to change their phone earlier than they planned or involved them paying to have the battery swapped.
Stuart Miles, founder and head of the Pocket-lint tech news website, was more sanguine about the research.
"As our demands on batteries become stronger and stronger, ensuring they can charge faster is at the forefront of everyone's focus," he said.
"A lot of what we do with our tech is limited by battery capabilities, but just imagine what could be achieved if we could top up our phones or computers in the same way we top up our cars with fuel."