Graphene hybrid for Supercapacitor
Unlike batteries, supercapacitors can quickly store large amounts of energy and release it just as fast. However, one problem with supercapacitors has been their low energy density — typically one tenth of the energy density achieved in lithium batteries (up to 265 kW/h). Now, an international team, working with Roland Fischer, professor of Inorganic and Metal-Organic Chemistry at the Technical University Munich (TUM; Germany; www.tum.de), has developed a highly efficient supercapacitor based on a sustainable graphene-hybrid material.
The TUM researchers developed a graphene hybrid material that serves as the positive electrode in supercapacitors, and combined this with a proven negative electrode based on titanium and carbon. The new energy storage device not only attains an energy density of up to 73 Wh/kg, which is roughly equivalent to the energy density of a nickel-metal-hydride battery. It also performs much better than most other supercapacitors at a power density of 16 kW/kg, according to TUM.
The researchers combined the novel positive electrode of the storage unit (with chemically modified graphene) with a nano-structured metal organic framework (MOF). This graphene hybrid has a large specific surface (up to 900 m2/g) and controllable pore sizes, as well as a high electrical conductivity. When used in a cell, the TUM material retained around 90% capacity after 10,000 cycles. For comparison, the useful life of a “classic” lithium accumulator is around 5,000 cycles, says TUM.
The research — performed in collaboration with scientists from India, Australia, Spain, the Czech Republic and the U.S. — was published in a recent issue Advanced Materials.