Deposition of thin conducting polymer coating on sulfur powder by dielectric barrier discharge (DBD)-plasma: positive materials for lithium sulfur batteries
“Among the different battery technologies under development, the lithium-sulfur (Li-S) batterie is one of the most promising and advanced. Li-S batteries reach today an energy density of 400 Wh/kg at pilot scale. However Li-S batteries still suffer from limited life-time and limited charge rate.
The presence of a conductive coating allows to mitigate the usual limitations of the Li-S batteries by improving the electron percolation in the sulfur electrode and by acting as a trapping barrier for the solubilized sulfur species. Standard sulfur coating methods are using wet procedure that are hardly up-scalable. We report an alternative approach to coat sulfur powder using a dry route, based on DBD-plasma technology with conducting polymers. Thin coating can be obtained at low temperature and ambient pressure compatible with sulfur elements. The absence of drying step, time & energy costly, limits the risk of aggregation phenomena. An intensive characterization of the coated-sulfur powder (NMR, Raman and XPS) confirms the presence of thin conducting polymers on the surface of the sulfur particles with a typical thickness of several nanometers. It is in agreement with a dramatic increase of its electrical conductivity in comparison to the pristine sulfur powder. Battery testing confirms that the presence of the PEDOT-coating allows to mitigate the capacity fading, to increase the charge rates and the electrochemical kinetics of the Li-S cells.”