Published On: Fri, Nov 4th, 2016

How to turn scrap metal into a ‘homemade’ battery

Engineers used bits of metal scraps and a household chemical to create the world’s first steel-brass battery that can store energy at levels comparable to lead-acid batteries. It also charges and discharges at rates comparable to ultra-fast charging supercapacitors.

“I believe we will see the day when residents will disconnect from the grid and produce their own batteries.”

In a paper published in the journal ACS Energy Letters, they describe the secret to unlocking the performance: anodization.

It’s a common chemical treatment used to give aluminum a durable and decorative finish.

When scraps of steel and brass are anodized using a common household chemical and residential electrical current, the researchers found that the metal surfaces are restructured into nanometer-sized networks of metal oxide that can store and release energy when reacting with a water-based liquid electrolyte.

“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,” says Cary Pint, assistant professor of mechanical engineering at Vanderbilt University.

Pint and colleagues determined that these nanometer domains explain the fast charging behavior that they observed, as well as the battery’s exceptional stability. They tested it for 5,000 consecutive charging cycles—the equivalent of over 13 years of daily charging and discharging—and found that it retained more than 90 percent of its capacity.

Unlike the recent bout of exploding lithium-ion cell phone batteries, the steel-brass batteries use non-flammable water electrolytes that contain potassium hydroxide, an inexpensive salt used in laundry detergent.

“When our aim was to produce the materials used in batteries from household supplies in a manner so cheaply that large-scale manufacturing facilities don’t make any sense, we had to approach this differently than we normally would in the research lab,” Pint says.

DIY batteries made at home?

The research team is particularly excited about what this breakthrough could mean for how batteries are made in the future.

“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 decentralized and scaled down to individuals or communities.

“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,” Pint says.

“We’re forging new ground with this project, where a positive outcome is not commercialization, but instead a clear set of instructions that can be addressed to the general public.”

The team drew inspiration from the “Baghdad Battery,” a simple device dating back to the first century BC, which some believe is the world’s oldest battery. It consisted of a ceramic terracotta pot, a copper sheet, and an iron rod, which were found along with traces of electrolyte.

Although this interpretation of the artifacts is controversial, the simple way they were constructed influenced the research team’s design.

The team’s next step is to build a full-scale prototype battery suitable for use in energy-efficient smart homes.

“We’re forging new ground with this project, where a positive outcome is not commercialization, but instead a clear set of instructions that can be addressed to the general public. 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,” Pint says.