Computational studies of polysulfides interaction with graphene oxide Structures

P. VÉLEZ; G. LUQUE; A. CALDERON ; D. BARRACO; E. P. M. LEIVA

Congreso; 20th Topical Meeting of the International Society of Electrochemistry Advances in Lithium and Hydrogen Electrochemical Systems for Energy Conversion and Storage, 19 al 22 Marzo 2017 Buenos Aires, Argentina; 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 elementalsulfur. The use of sulfur also present the great advantages such as being environmental friendly, greatnatural abundance, low cost and wide operating temperature range.Nevertheless the usage of sulfur present the disadvantages of being insulating, also, the anode and thecathode suffers from volume changes during cycling and the polysulfides intermediates that are generateddiffuse 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 forthe retention of polysulfides. In this sense, graphene oxide membranes show a great promise blocking thepolysufide transportation. Here we present ab initio density functional studies of the interaction ofgraphene 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 considerationaltered oxygen functionalities. We mainly study long chain polysulfides (Li 2 S 6 and Li 2 S 8 ) and itsinteraction with the different graphene oxide structures. We performed optimization geometries of thosesystems 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 oxideinteracting with Li 2 S 6 polysulfide.