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Better conductivity increases battery efficiency

Posted: 14 Apr 2015 ?? ?Print Version ?Bookmark and Share

Keywords:University of South Carolina? battery? fuel cell? gadolinium doped ceria?

University of South Carolina and Clemson University researchers have found a method that promises to enhance the efficiency of batteries and fuel cells by using the material gadolinium doped ceria (GDC). The research, which is published in the journal Nature Communications, involves improving the transport of oxygen ions, which is an essential component in converting chemical energy into electricity.

The researchers studied GDC, which transports oxygen ions and is being used as a solid oxide fuel cell electrolyte. Through the use of additives and a 'smart' chemical reaction, they demonstrated an enhanced conductivity in GDC. The result is a faster and more efficient conversion into electricity.

"This breakthrough will pave the path to fabricate next generation energy conversion and storage devices with significantly enhanced performance, increasing energy efficiency and making energy environmentally benign and sustainable," explained Fanglin (Frank) Chen, a mechanical engineering professor in the University of South Carolina's College of Engineering and Computing.

"The origin of the low grain boundary conductivity is known to be segregation of gadolinium (Gd) in the grain boundary which leads to a built-in charge at the interface referred to as the space charge effect," said Chen. "This built in charge serves as a barrier for ion transport at the interface. The challenge is how to effectively avoid the segregation of Gd in the grain boundary. The grain boundary is extremely narrow, on the order of a few nanometres. Therefore, it is extremely difficult to characterise and rationally control the amount of Gd in such a narrow region."

"In order to make 'clean' grain boundaries and avoid the segregation of Gd at the interface we have added an electronic conductor cobalt iron spinel (CFO), resulting in a composite structure," said Kyle Brinkman, a materials science and engineering professor at Clemson University and co-corresponding author of the work. "The CFO reacts with the excess Gd present in the grain boundary of GDC to form a third phase. It was found that this new phase could also serve as an excellent oxygen ionic conductor. We further investigated the atomic microstructure around the grain boundary through a series of high resolution characterisation techniques and found that Gd segregation in the grain boundary had been eliminated, leading to dramatic improvement in the grain boundary oxygen ionic conductivity of GDC."

The improved oxygen ionic conductivity of GDC has been demonstrated in an oxygen permeation experiment where the elevated oxygen ion transport was used to separate pure oxygen from air at elevated temperatures. The approach of targeting emergent phases resulting in clean interfaces can be applied to a number of essential materials for energy conversion and storage devices used in handheld electronics, vehicles and power plants, making them more cost-effective, efficient and environmentally friendly.

- Paul Buckley
??EE Times Europe

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