Take some metal scraps from the junkyard; put them in a glass jar with a common household chemical; and, voil脿, you have a high-performance battery.
鈥淚magine 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,鈥� said , assistant professor of mechanical engineering at Vanderbilt University.
To make such a future possible, Pint headed a research team that used scraps of steel and brass 鈥� two of the most commonly discarded materials 鈥� to create the world鈥檚 first steel-brass battery that can store energy at levels comparable to lead-acid batteries while charging and discharging at rates comparable to ultra-fast charging supercapacitors.
The research team, which consists of graduates and undergraduates in Vanderbilt鈥檚 interdisciplinary materials science program and department of mechanical engineering, describe this achievement in a paper titled 鈥溾�� published online this week in the journal .
The secret to unlocking this performance is anodization, 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.
The team determined that these nanometer domains explain the fast charging behavior that they observed, as well as the battery鈥檚 exceptional stability. They tested it for 5,000 consecutive charging cycles 鈥� the equivalent of over 13 years of daily charging and discharging 鈥� 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.
鈥淲hen our aim was to produce the materials used in batteries from household supplies in a manner so cheaply that large-scale manufacturing facilities don鈥檛 make any sense, we had to approach this differently than we normally would in the research lab,鈥� Pint said.
The research team is particularly excited about what this breakthrough could mean for how batteries are made in the future.
鈥淲e鈥檙e seeing the start of a movement in contemporary society leading to a 鈥榤aker culture鈥� 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 [lquote]I believe we will see the day when residents will disconnect from the grid and produce their own batteries.[/lquote] That鈥檚 the scale where battery technology began, and I think we will return there,鈥� Pint said.
The Vanderbilt team drew inspiration from the 鈥淏aghdad Battery,鈥� a simple device dating back to the first century BC, which some believe is the world鈥檚 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鈥檚 design.
The team鈥檚 next step is to build a full-scale prototype battery suitable for use in energy-efficient smart homes.
鈥淲e鈥檙e 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鈥檚 a completely new way of thinking about battery research, and it could bypass the barriers holding back innovation in grid scale energy storage,鈥� Pint said.
Co-authors on this project include and who co-led the project and are graduate students in the interdisciplinary materials science program, Nicholas Galioto and Haotian Sun, who are both Vanderbilt mechanical engineering undergraduate students; and, who are graduate students in mechanical engineering; and , who is a graduate student in the interdisciplinary materials science program.
The work was supported by the EPSCoR grant NNX13AB26A, the graduate fellowship program under grant 1445197 and a Vanderbilt Discovery Grant. The team worked with Matt McCarthy at PSC Metals, who provided access to its scrap metal facility in support of this project.