A Nanomaterial which Acts as a Battery and a Supercapacitor Too

Covalent organic framework (COF). Credit: Northwestern University

Covalent organic framework (COF). Credit: Northwestern University

A powerful novel nanomaterial developed by Northwestern University chemist William Dichtel and his research team is going to be a game-changer in the field of electric charge storage and discharge technique. It can bring revolution in the electric car battery technology. An electric car relies on a very complex interplay of both batteries and supercapacitors to provide the energy it needs, but with this material can speed up the charging process of electric cars and help increase their driving range.

The material can be called as best of both worlds, which acts as both battery and a super capacitor, but the best capacities of both are combined in it – holding a large charge like batteries and very fast discharge like super-capacitors. Though battery and capacitor basically store electric charge, there are crucial differences between the two. The potential energy in a capacitor is stored in an electric field, where a battery stores its potential energy in a chemical form.

Dichtel and his team have integrated covalent organic frameworks (COFs), – strong, rigid polymers with plenty of minute pores ideal for storing energy – with a highly conductive material to develop the first altered “redox-active COF” that shortens the gap with other past porous carbon-based electrodes. A conductive polymer (green) formed inside the small holes of a hexagonal framework (red and blue) works with the framework to store electrical energy rapidly and efficiently.

COFs were always known to have beautiful porous structures with a lot of promise to the researchers in the organic chemistry, but their conductivity was limited, Northwestern University researchers have addressed the same problem successfully. They claim their material is capable of 10,000 charge / discharge cycles before stability is a concern. The modified redox-active COFs can store 10 times the electrical energy than that of an unmodified COFs. Also can move that charge in and out between 10 and 15 times faster.

These altered COFs are commercially appealing, as they are made using low-cost, easily available materials, while carbon-based materials used in capacitors and batteries are very costly to fabricate and produce on a mass scale and need to have bulky structures. The team made the material on an electrode surface, two organic molecules were self-assembled and condensed into a honeycomb-like grid with an organic chemical reaction, one 2-D layer stacked on top of the other. Into the grid’s holes or pores, the researchers deposited the conducting polymer.

While demonstrating new material’s capabilities, researchers built a coin-cell battery prototype device capable of powering a light-emitting diode for 30 seconds.

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