A new laser-based technique for making flexible, durable and highly conductive electrochemical capacitors
Advances in delivering and storing electricity are crucial to the future of electric cars and otherwise reducing reliance on energy produced from burning fossil fuels. Yet a powerful means of running electronics that can charge and discharge quickly while also storing large amounts of energy has long eluded scientists.
This predicament could be changing, thanks to new research. A team from the University of California, Los Angeles (UCLA), and Egypt’s Cairo University describe in the March 16 issue of Science a new laser-based technique for making flexible, durable and highly conductive electrochemical capacitors—also known as ultracapacitors or supercapacitors—out of graphene. Electrochemical capacitors handle frequent charge/discharge cycles well but have been unable to store lots of energy. (Lithium-ion and other conventional batteries can store large amounts of energy but have short life cycles and are filled with hazardous chemicals known to catch fire under certain conditions.)
Electrochemical capacitors made using graphene—a one-atom-thick sliver of graphite—began showing potential to boost storage capacity a few years ago. Individual graphene sheets create a larger surface area than when they are stacked together as a piece of graphite. This larger surface area increases energy storage capacity. Yet the strong electrostatic attraction between graphene sheets makes graphene a difficult material to work with because it tends to cause them to stack back together into their original graphite form.
The researchers, led by UCLA Ph.D. candidate and Cairo lecturer Maher El-Kady and Richard Kaner, a professor in UCLA’s Chemistry & Biochemistry and Material Sciences & Engineering departments, found a way to avoid this re-stacking. They covered an ordinary compact disk with a sheet of plastic, coated that plastic with graphite oxide and used a LightScribe DVD optical drive to locally heat the coating to turn it into a graphene film that can store energy in a highly-reversible electrical form important for many present and emerging applications.
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