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nanotimes News in Brief Batteries //

Improved Batteries with Carbon Nanoparticles © Based on Material by LMU, Germany

I

n an important step toward the further develop- ment of batteries, a team led by Professor Thomas

Bein of LMU Munich and Linda Nazar of Waterloo University in Canada has developed porous carbon nanoparticles that utilize sulfur molecules to achie- ve the greatest possible efficiency. To improve the battery’s design the scientists at Nanosystems Initi- ative Munich (NIM) strive to generate sulfur phases with the greatest possible interface area for electron transfer by coupling them with a nanostructured con- ductive material.

To this end, Thomas Bein and his team at NIM first developed a network of porous carbon nanoparti- cles. The nanoparticles have 3- to 6-nanometer wide pores, allowing the sulfur to be evenly distributed. In this way, almost all of the sulfur atoms are available to accept lithium ions. At the same time they are also located close to the conductive carbon.

“The sulfur is very accessible electrically in these novel and highly porous carbon nanoparticles and is stabilized so that we can achieve a high initial capacity of 1200 mAh/g and good cycle stability,” explains Thomas Bein. “Our results underscore the significance of nano-morphology for the performance of new energy storage concepts.”

The carbon structure also reduces the so-called poly- sulfide problem. Polysulfides form as intermediate

products of the electrochemical processes and can have a negative impact on the charging and dischar- ging of the battery. The carbon network binds the polysulfides, however, until their conversion to the desired dilithium sulfide is achieved. The scientists were also able to coat the carbon material with a thin layer of silicon oxide which protects against polysul- fides without reducing conductivity.

/g) of all mesoporous carbon nanoparticles, and an extremely large surface area of 2445 m2

/g. This

corresponds roughly to an object with the volume of a sugar cube and the surface of ten tennis courts. Large surface areas like this might soon be hidden inside our batteries.

Joerg Schuster, Guang He, Benjamin Mandlmeier, Taeeun Yim, Kyu Tae Lee, Thomas Bein, Linda F. Nazar: Spherical Ordered Mesoporous Carbon Nanoparticles with High Po- rosity for Lithium-Sulfur Batteries, In: Angewandte Chemie International Edition, Volume 51, Issue 15, April 10, 2012, Pages 3591-3595, DOI:10.1002/anie.201107817: http://dx.doi.org/10.1002/anie.201107817

http://bein.cup.uni-muenchen.de

Incidentally, the scientists have also set a record with their new material: According to the latest data, their material has the largest internal pore volume (2.32 cm3

12-03 :: March/April 2012