Computational studies of polysulfides interaction with graphene oxide Structures

PATRICIO VÉLEZ, ; GUILLERMINA LUQUE; ANDREA CALDERÓN; DANIEL BARRACO, ; EZEQUIEL LEIVA

Congreso; 20th Topical Meeting of the International Society of Electrochemistry Advances in Lithium and Hydrogen Electrochemical Systems for Energy Conversion and Storage; 2017

Lithium−sulfur present great attention nowadays due to its high specific capacity and energy density. The great energy storage is accomplished through the phase transformation chemistry based on elemental sulfur. The use of sulfur also present the great advantages such as being environmental friendly, great natural abundance, low cost and wide operating temperature range. Nevertheless the usage of sulfur present the disadvantages of being insulating, also, the anode and the cathode suffers from volume changes during cycling and the polysulfides intermediates that are generated diffuse between cathode and anode causing side reactions conducting to low Coulombic efficiency, self-discharge and fast fading capacity. In order to solve this last issue, the utilization of permselective membranes present as a great result for the retention of polysulfides. In this sense, graphene oxide membranes show a great promise blocking the polysufide transportation. Here we present ab initio density functional studies of the interaction of graphene oxide with long-chain polysulfides as a possible membrane to prevent the shuttle mechanism. The computational studies were carried on with SIESTA. We made different studies with different levels of graphene oxidation and taking into consideration altered oxygen functionalities. We mainly study long chain polysulfides (Li2S6 and Li2S8) and its interaction with the different graphene oxide structures. We performed optimization geometries of those systems and performed Mulliken population analysis, pseudo charge densities and density of states (DOS) studies. The next figure illustrates the unit cell considered for one of this systems: graphene oxide interacting with Li2S6 polysulfide.