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A supercapacitor with improved performance

Researchers from the IISc have developed a graphene-based 'supercapacitor' with superior performance.

Capacitors are everywhere: from mobile phones to FM radios to computer mother boards. In fact, it is hard to imagine a useful electronic circuit without a capacitor. Supercapacitors, as the name indicates, are capacitors that can store a lot of energy in the form of electric charge.

“Supercapacitors can be used to construct portable electronics, digital communications, electric vehicles, hybrid electric vehicles devices and other renewable energy systems. We could also use for regenerative braking, short-term energy storage in applications requiring many rapid charge/discharge cycles”, explains Dr S Shivakumara, who is part of the team that carried out the study.

Supercapacitors are similar to batteries in function, but much better in performance. They can store energy, can be charged quickly, and can be taken through tens of thousands charge-discharge cycles. Graphene, the new material with exceptional electrical, mechanical and electrochemical properties, is known to improve supercapacitor performance. However, these devices are still in development stage, and when they hit the market, they are expected to improve overall performance of energy systems.

The IISc researchers inserted oxygen functionalities between layers of graphite. They removed oxygen to obtain what is called the 'reduced graphene oxide' with a few oxygen functionalities left on the surface. These functionalities, according to them, have a positive impact on the electrochemical properties of the reduced graphene oxide. They built a supercapacitor using a combination of three different solvents and a lithium salt as the electrolyte. Under suitable conditions, salt dissolves and furnishes positive and negative charges, and hence conducts electricity. Without them, our vehicle batteries and supercapacitors don't work.

An analysis of the performance of the supercapacitor revealed that its performance is superior to others in the same category. To test the device, the researchers took it through three thousand charge-discharge cycles, and the device's performance remained quite stable.

Encouraged by this result, the researchers want to see how they could improve the commercially available lithium ion batteries. “Lithium ion batteries use graphite in their negative terminal, and we want to see if we can replace them with reduced graphene oxide. We also plan to prepare hybrid electrode materials by combining with the metals, metal oxides for future energy storage applications”, says Dr S Shivakumara.

About the authors:

N. Munichandraiah is a Professor in the Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore. Dr S Shivakumara is a Post-Doctoral fellow at Munichandraiah's laboratory. Brij Kishore and Tirupathi Rao Penki are PhD students in the same laboratory.

Contact:

Dr S Shivakumara: elessk@gmail.com

Prof. N. Munichandraiah: 080 2293 3183; muni@ipc.iisc.ernet.in

About the paper:

This paper appeared in ECS Electrochemical Letters and can be accessed at http://eel.ecsdl.org/content/4/8/A87.full

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IPC