AsianScientist (Feb. 19, 2019) – A research group at Tohoku University, Japan, has developed materials for supercapacitors with higher voltage and better stability. Their findings are published in the journal Energy and Environmental Science.
Supercapacitors are rechargeable energy storage devices with a broad range of applications, from machinery to smart meters. They offer many advantages over batteries, including faster charging and longer lifespans, but they are unable to store large amounts of energy.
Scientists have long been looking for high-performance materials for supercapacitors that can meet the requirements for energy-intensive applications such as cars.
“It is very challenging to find materials which can both operate at high voltage and remain stable under harsh conditions,” said Dr. Hirotomo Nishihara, materials scientist at Tohoku University.
Hence, Nishihara and colleagues collaborated with the supercapacitor production company TOC Capacitor Co. to develop a material that exhibits high stability under conditions of high voltage and high temperature.
In this study, Nishihara’s team made a sheet from a continuous three-dimensional framework of graphene mesosponge, a carbon-based material containing nanoscale pores. A key feature of the material is that it is seamless—it contains a very small amount of carbon edges, the sites where corrosion reactions originate—making it extremely stable.
The researchers investigated the physical properties of their material using electron microscopy and a range of physical tests, including X-ray diffraction and vibrational spectroscopy techniques. They also tested commercial graphene-based materials, including single-walled carbon nanotubes, reduced graphene oxides and 3D graphene, using activated carbons as a benchmark for comparison.
They showed that their material had excellent stability at high temperatures of 60°C and high voltage of 3.5 volts in a conventional organic electrolyte. Significantly, it showed ultra-high stability at 25°C and 4.4 volts, 2.7 times higher than conventional activated carbons and other graphene-based materials.
Because the graphene mesosponge has higher single-cell voltage, fewer cells need to be stacked together to achieve the desired voltage, thereby allowing devices to be more compact.
“This is a world record for voltage stability of carbon materials in a symmetric supercapacitor,” said Nishihara.
The new material paves the way for development of highly durable, high-voltage supercapacitors that could be used for many applications, including motor vehicles, the researchers added.
The article can be found at: Nomura et al. (2019) 4.4 V Supercapacitors Based on Super-stable Mesoporous Carbon Sheet Made of Edge-free Graphene Walls.
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Source: Tohoku University; Photo: Hirotomo Nishihara.
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