Polysulfides interaction with functionalized graphene structures

GUILLERMINA LUQUE; MARIA ROJAS; VICTORIA BRACAMONTE; EZEQUIEL LEIVA; PATRICIO VELEZ; MANUEL OTERO; GERMAN LENER; LAURA PARA; EMILIANO PRIMO; DANIEL BARRACO

Chicago

Congreso; 10th International Conference on Advanced Lithium Batteries for Automobile Applications; 2017

Recently, lithium-sulfur (Li-S) batteries have attracted a lot of attention, due to its high theoretical capacity and high energy density of sulfur, its natural abundance, low cost and environmental friendliness. Nevertheless, Li-S batteries suffer from different problems, such as the insulating nature of sulfur, the generation of polysulfides during the charge/discharge reaction that dissolve in the electrolyte producing low utilization of the active material and capacity fading, the change of volume of the active material, and the polysulfide shuttling effect that causes low charge/discharge efficiency and corrosion of the lithium anode. To overcome these issues, there are different approaches, such as, incorporation of conductive matrices and adsorbent agents in the cathode, optimization of new electrolytes, modification of the separator to reduce the shuttle effect, the protection of lithium anode with polymers, among others.To overcome the issue of the shuttle effect, there are at present day, different studies that propose the use of modified carbon materials in the separators or in the cathode material. In the present work we present the study of the interaction of long chain polysulfides with graphene modified by different functional groups that can be either used as cathode material or separator. These were performed through ab initio functional studies using SIESTA [1]. The results found help in the understanding of the type of interactions that takes place among the different modified structures and the polysulfides and will help finding the optimal material in order to obtain a high capacity, Coulombic efficiency, and long cycle life battery.We performed optimization geometries, Mulliken population analysis, pseudo charge densities and density of states (DOS) studies of the different functionalized graphene structures whit the long chain polysulfides.