COF William Dichtel
A conductive polymer (green) formed inside the small holes of a hexagonal framework (red and blue) work together to store electrical energy rapidly and efficiently.

University Chemist and Team Develop New Electrical Energy Storage Material

The material could one day speed up the charging process of electric cars and help increase their driving range

A powerful new material developed by Northwestern University chemist William Dichtel and his research team could one day speed up the charging process of electric cars and help increase their driving range. Dichtel and his research team have combined a COF – a strong, stiff polymer with an abundance of tiny pores suitable for storing energy – with a very conductive material to create the first modified redox-active COF that closes the gap with other older porous carbon-based electrodes.

“Our material combines the best of both worlds – the ability to store large amounts of electrical energy or charge, like a battery, and the ability to charge and discharge rapidly, like a supercapacitor,” said Dichtel, a pioneer in the young research field of covalent organic frameworks (COFs).

According to a news story from Northwestern's campus news, this nanomaterial combines the attributes of both batteries and supercapacitors. The report states that modified COFs are commercially attractive: COFs are made of inexpensive, readily available materials, while carbon-based materials are expensive to process and mass-produce.

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

The material has outstanding stability, capable of 10,000 charge/discharge cycles, the researchers report. They also performed extensive additional experiments to understand how the COF and the conducting polymer, called poly(3,4-ethylenedioxythiophene) or PEDOT, work together to store electrical energy. 

Dichtel and his team made the material on an electrode surface. Two organic molecules self-assembled and condensed into a honeycomb-like grid, one 2-D layer stacked on top of the other. Into the grid’s holes, or pores, the researchers deposited the conducting polymer.

Each pore is only 2.3 nanometers wide, but the COF is full of these useful pores, creating a lot of surface area in a very small space. A small amount of the fluffy COF powder, just enough to fill a shot glass and weighing the same as a dollar bill, has the surface area of an Olympic swimming pool.

The modified COF showed a dramatic improvement in its ability to both store energy and to rapidly charge and discharge the device. The material can store roughly 10 times more electrical energy than the unmodified COF, and it can get the electrical charge in and out of the device 10 to 15 times faster.

The research was conducted at Cornell University, where Dichtel was a faculty member until this summer, when he moved to Northwestern.

 

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