Carbon Nanofiber Improves Lithium Air Battery Storage Capacity

Researchers at MIT have been successful in developing higher energy density Lithium-air batteries which is more efficient than its cousin Lithium-ion battery. The new batteries being developed in laboratory of MIT may soon become the powering device for future thereby replacing the now commercially available Lithium Ion batteries.

#-Link-Snipped-#The present day Lithium ion batteries are made up of solid carbon electrodes which although efficient are not porous like the new Lithium air batteries. According to the researchers, this only adds unnecessarily to the weight of battery. The new energy storage devices are in reality continuation of last year's work by MIT scientists in which they had made efficient carbon electrodes. Taking a step ahead, the people at MIT have developed a carbon fiber based electrodes which will provide pores Solid Lithium oxide that accumulates in the pores as the battery discharges. The pores present in the conventional Lithium ion batteries are very minute to perform the job effectively.

In the research, the method designed by scientists’ means, growing vertically aligned arrays of carbon nanofibers, using Chemical vapor deposition process. This produces carpet like porous, high energy density electrodes. The void space so available accounts for 90% of electrode. This is an improvement as compared to last year which had 70% available void space. The structure although efficient than conventional batteries was however little more complex. The empty space traps oxygen from the air flowing through system and oxidizes lithium present in the pores to form Li peroxide.

#-Link-Snipped-#
This diagram depicts the essential functioning of the lithium-air battery. Ions of lithium combine with oxygen from the air to form particles of lithium oxides, which attach themselves to carbon fibers on the electrode as the battery is being used. During recharging, the lithium oxides separate again into lithium and oxygen and the process can begin again.

The electrodes formed by using carbon nanofibers are very orderly which is very different from the haphazardly placed carbon in regular electrodes. The structure is evident from the scanning electron microscope. The microscope is very helpful in observing the characteristics of intermediately charged electrodes.

The gravimetric studies done in this aspect holds that the new approach is an effective way to improve the overall performance of the batteries. The newer version of Li batteries is yet to be commercialized. The research work in this aspect is published in journal Energy and Environmental Science. The paper is authored by Yang Shao-Horn, the Gail E. Kendall Professor of Mechanical Engineering and Materials Science and Engineering, MIT graduate students Robert Mitchell and Betar Gallant.

Source: #-Link-Snipped-#