Homemade metal-scraps battery charges at rocket speed
Image credit: Vanderbilt University
A battery that charges at a similar rate to ultra-fast charging supercapacitors and offers energy storage capacity equivalent to that of lead-acid batteries has been created from junkyard metal scraps and laundry detergent salt.
The device, designed by a team of mechanical engineers from Vanderbilt University in the USA, loses only 10 per cent of its capacity after 5000 consecutive charging cycles, equivalent to 13 years of daily usage. Unlike lithium-ion batteries, the junkyard battery doesn’t pose any risk of explosion or ignition as it only contains non-flammable water electrolytes based on potassium hydroxide, which is commonly used in laundry detergents.
“Imagine that the tons of metal waste discarded every year could be used to provide energy storage for the renewable energy grid of the future, instead of becoming a burden for waste processing plants and the environment,” said Cary Pint, assistant professor of mechanical engineering at Vanderbilt University.
The key to the battery’s performance is in the treatment of the steel and brass scraps. Using a technique that could be replicated by anyone at home, the researchers anodised the scraps’ surface. This resulted in nanometre-scale metal oxide structures that can store and release energy when reacting with a water-based liquid electrolyte.
The researchers say they aren't aiming to commerecialise their invention. Instead, they would like to make the know how publically available to enable people to build their own batteries for domestic use.
“We’re seeing the start of a movement in contemporary society leading to a ‘maker culture’ where large-scale product development and manufacturing is being decentralised and scaled down to individuals or communities,” Pint said.
“So far, batteries have remained outside of this culture, but I believe we will see the day when residents will disconnect from the grid and produce their own batteries. That’s the scale where battery technology began, and I think we will return there.”
The researchers named the world’s oldest known battery – the so called Baghdad Battery from the first century BC – as their inspiration. Although some doubt whether it really was a battery, this device consisted of a ceramic terracotta pot, a copper sheet and an iron rod found alongside traces of electrolyte.
Instead of a terracotta pot, the Vanderbilt team used a regular glass jar.
“We’re forging new ground with this project, where a positive outcome is not commercialisation, but instead a clear set of instructions that can be addressed to the general public,” said Pint. “It’s a completely new way of thinking about battery research, and it could bypass the barriers holding back innovation in grid-scale energy storage.”
The researchers described the invention in an article in the journal ACS Energy Letters. The team is currently working on a full-scale prototype battery suitable for use in energy-efficient smart homes.