Waste industrial cotton and sea water can make costly parts of a Supercapacitor: Indian research scientists

Can a supercapacitor be prepared from waste or from something which is almost free? Seems amazing or unbelievable. Well, Indian scientists have developed a technology to make a simple, low-cost environmentally friendly and sustainable supercapacitor electrode derived from industrial waste cotton, and an electrolyte for a Supercapacitor derived from seawater.

Both these products electrodes and electrolyte for a supercapacitor is not only environmentally friendly and cost-effective, but also a scalable, and alternative aqueous electrolyte, which may replace the existing aqueous-based electrolytes for the economic fabrication of supercapacitor, claim the scientists of the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), an autonomous organization of the Department of Science and Technology, Govt. of India, which had invented these two costly components from waste.

Supercapacitor:

A supercapacitor (SC), also called an ultracapacitor  with a capacitance value much higher than other capacitors, but with lower voltage limits, that bridges the gap between electrolytic capacitors and rechargeable batteries. It typically stores 10 to 100 times more energy per unit volume or mass than electrolytic capacitors, can accept and deliver charge much faster than batteries, and tolerates many more charges and discharge cycles than rechargeable batteries.

It is a next-generation energy storage device that has received extensive research attention owing to advantages such as high power density, long durability, and ultrafast charging characteristic as compared to conventional capacitors and lithium-ion batteries (LIB).

Its Usage:

Supercapacitors are used in applications requiring many rapid charge/discharge cycles, rather than long term compact energy storage — in automobiles, buses, trains, cranes and elevators, where they are used for regenerative braking, short-term energy storage, or burst-mode power delivery, smaller units can be used as a power backup for static random access memory (SRAM).

 

The Invention:

Scientists from ARCI, an autonomous organization of the Department of Science and Technology, Govt. of India, has developed these two low-cost, environmentally friendly, and sustainable supercapacitor electrode derived from industrial waste cotton and electrolyte from natural seawater which may replace the existing aqueous-based electrolytes for the economic fabrication of supercapacitor.

 

A supercapacitor has four components (1) electrode, (2) electrolyte, (3) separator, and the (4) current collector. The first two, electrode and electrolyte, developed by the scientists of ARCI, are the pivotal components. And it directly determines the electrochemical behaviour of the supercapacitors and is considered to be very costly components.

The fabrication cost of electrode materials, as well as electrolytes, should be reduced because these two components account for the cost of the device. In search of a cost-effective material for making affordable supercapacitor devices, scientists at ARCI have converted industrial waste cotton (Trash) into highly porous carbon fibers (Treasure) by activation process and then utilised the porous carbon fibers to make high-performance supercapacitor electrodes.

In the recent research published in Energy Technology, scientists at ARCI demonstrated the feasibility of using seawater as natural electrolyte for the fabrication of aqueous-based supercapacitor devices which shows great potential for practical implementation. The study found that natural seawater-based supercapacitor exhibited maximum capacitances at a current density of 1 Ag^-1. In addition, seawater-based supercapacitor shows very good durability upon 10,000 charge-discharge cycles with 99 % of capacitance retention and 99 % of Coulombic efficiency (efficiency with which charge is transferred in a system facilitating an electrochemical reaction).

The research team’s new, sustainable and green supercapacitor device shows great potential for practical application, and perhaps most importantly, the integrated solar cell with seawater-based supercapacitor as low cost, eco-friendly, efficient and self-powering device.

The successful demonstration of the device revealed that solar-powered supercapacitors can not only store the electrical energy but also overcome the drawbacks of the intermittent nature of the solar irradiation. Hence, the integrated solar cell with supercapacitor can be used as an energy harvester storage device due to their long cycle life and maintenance-free power supply. 

“The large-scale use of renewable energy requires the creation of matching capacity for inexpensive electrical energy storage. This study provides a solution for the fabrication of super-capacitors from such abundant materials as waste cotton and seawater! It is an excellent example of the creative science for the sustainable, green processes embedding principles of waste-to-wealth,” says Prof Ashutosh Sharma, Secretary, DST.

BY Vijay Thakur, Special Representative, The Statesman, vijaythakurx@gmail.com

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