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Power up the supercapacitor!

lightning bolt cartoon
Consider please, the supercapacitor. To the uninitiated, the word conjures the image of something futuristic and powerful. It sounds almost like it should be featured in a comic or a piece of kit in a 1960s space adventure series. But these devices are not imaginary – they exist and may actually be the key to clean energy for future transport systems across the world.

Evé Wheeler Jones, a PhD researcher at WMG, University of Warwick explains: “Supercapacitors are super high power energy storage devices. Just like batteries, they are charged and discharged and can store energy. However, a supercapacitor uses a different mechanism to store charge, meaning they have higher power, shorter charge times and longer lifetimes than batteries. They also have a lower energy density – the measure of how much energy can be stored – when compared to a battery. Because of this, supercapacitors currently have slightly different applications. They are often used for smoothing current in the grid, safety systems, and in wind turbines.

“But, new research is showing that supercapacitors may be able to rival batteries. In China, they are already being used to power electric buses.”

The battery has a rival

Evé is working on a research project looking at developing new materials for high power storage devices. The research aims to increase the energy density of the supercapacitor so it could begin to rival the battery.

She explains: “My work looks at using metal oxide materials to increase the energy density of devices. Metal oxides have been used in both supercapacitors and batteries, and so are perfect for a new type of device called a hybrid supercapacitor, which has the best properties of both types of device. A successful supercapacitor material needs to have a high surface area, as the charge is stored at the surface. So I have been developing new synthesis methods to make high surface area metal oxides.”

Evé’s work has included making particles that look like wire, but on a nano scale with a width of approximately 10 nm - about 1000 times thinner than a human hair.

Successful synthesis

“When developing these materials the first step is to develop a successful synthesis method,” explains Evé. “For me this includes using acids and pressure vessels. The material then needs to be characterised, this analyses the material to find exactly what has been made and what properties the material has. I use an X-ray Diffractometer which fires X-rays at the material and detects the light that is scattered off to create a pattern, which is like a fingerprint for the material. The material can also be observed under an electron microscope, which helps to identify the size and shape of the particles. Importantly the surface area can also be measured using a ‘nitrogen sorption’ machine, where nitrogen gas is injected into the material. The amount injected can then be used to calculate the surface area.

“This work is important to understand what the material is and what properties it should have, but it is only the first stage. It is not until you build the material into a supercapacitor device that you can begin to understand whether it is a good material for energy storage.”

Promising materials

metal oxide materialsEvé is currently at the stage in her research where she has synthesised many different promising metal oxide materials.

“Some of these materials look like wires at the nano scale, some of these look like spheres and I have even worked on trying to decorate the nanowire with the spherical particles too, in order to make the most of the different types of materials.

“The materials I have made look promising as they have high surface areas when compared to what has developed before, however, the tests on these materials as energy storage devices are still in the early stages,” she says. “But it is exciting to think one of these new metal oxide materials could hold the key to a new type of energy device which could transform the world of electric vehicles.”

 

Published:

21 June 2019

About:

Eve Wheeler-Jones

Evé Wheeler-Jones is a PhD researcher at WMG, University of Warwick. She has a BSc in Chemistry and an MSc in analytical science. Her PhD research is on synthesis of new materials for high power energy storage. She is a student representative on the WMG Athena Swan committee and has a passions for outreach and public engagement and takes an active role participating in events like Pint of Science and the Warwick Christmas Lecture series.

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