Stanford engineers create a low-cost battery for storing renewable energy
Stanford engineers create a low-cost battery for storing
renewable energy
A new low-cost, high-performance battery could provide an
inexpensive storage solution for solar power, which is abundant during the day
but must be stored for use at night.
BY JACKIE FLYNN FEBRUARY 7, 2017
A battery made with urea, commonly found in fertilizers
and mammal urine, could provide a low-cost way of storing energy produced
through solar power or other forms of renewable energy for consumption during
off hours.
Developed by Stanford chemistry Professor Hongjie Dai and
doctoral candidate Michael Angell, the battery is nonflammable and contains
electrodes made from abundant aluminum and graphite. Its electrolyte’s main
ingredient, urea, is already industrially produced by the ton for plant
fertilizers.
“So essentially, what you have is a battery made with
some of the cheapest and most abundant materials you can find on Earth. And it
actually has good performance,” said Dai. “Who would have thought you could
take graphite, aluminum, urea, and actually make a battery that can cycle for a
pretty long time?”
In 2015, Dai’s lab was the first to make a rechargeable
aluminum battery. This system charged in less than a minute and lasted
thousands of charge-discharge cycles. The lab collaborated with Taiwan’s
Industrial Technology Research Institute (ITRI) to power a motorbike with this
older version, earning Dai’s group and ITRI a 2016 R&D 100 Award. However,
that version of the battery had one major drawback: it involved an expensive
electrolyte.
The newest version includes a urea-based electrolyte and
is about 100 times cheaper than the 2015 model, with higher efficiency and a
charging time of 45 minutes. It’s the first time urea has been used in a
battery. According to Dai, the cost difference between the two batteries is
“like night and day.” The team recently reported its work in Proceedings of the
National Academy of Sciences.
Renewable energy storage
Unlike energy derived from fossil fuels, solar energy can
essentially be harnessed only when the sun is shining. A solar panel pumps
energy into the electrical grid during daylight hours. If that energy isn’t
consumed right away, it is lost as heat. As the demand for renewable
technologies grows, so does the need for cheap, efficient batteries to store
the energy for release at night. Today’s batteries, like lithium-ion or lead
acid batteries, are costly and have limited lifespans.
Dai and Angell’s battery could provide a solution to the
grid’s storage problem.
“It’s cheap. It’s efficient. Grid storage is the main
goal,” Angell said.
According to Angell, grid storage is also the most
realistic goal, because of the battery’s low cost, high efficiency and long
cycle life. One kind of efficiency, called Coulombic efficiency, is a
measurement of how much charge exits the battery per unit of charge that it
takes in during charging. The Coulombic efficiency for this battery is high –
99.7 percent.
Though also efficient, lithium-ion batteries commonly
found in small electronics and other devices can be flammable. By contrast,
Dai’s urea battery is not flammable and therefore less risky.
“I would feel safe if my backup battery in my house is
made of urea with little chance of causing fire,” Dai said.
The group has licensed the battery patents to AB Systems,
founded by Dai. A commercial version of the battery is currently in
development.
Future directions
To meet the demands of grid storage, a commercial battery
will need to last at least ten years. By investigating the chemical processes
inside the battery, Angell hopes to extend its lifetime. The outlook is
promising. In the lab, these urea-based aluminum ion batteries can go through
about 1,500 charge cycles with a 45-minute charging time.
According to Dai, there is plenty of demand for a
grid-suitable battery; he receives numerous emails from firms or individuals
interested in developing aluminum batteries. And with the battery now in
development, its success rests on the interest of companies and consumers.
“With this battery, the dream is for solar energy to be
stored in every building and every home,” Dai said. “Maybe it will change
everyday life. We don’t know.”
This research was supported by the Department of Energy,
The Global Networking Talent 3.0 Plan, the Ministry of Education of Taiwan and
the Taishan Scholar Project. Additional co-authors include Chun-Jern Pan,
Youmin Rong, Chunze Yuan, Meng-Chang Lin and Bing-Joe Hwang.
Media Contacts
Amy Adams, Stanford News Service; (650) 796-3695, amyadams@stanford.edu
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