Despite dominating the current commercial energy storage landscape, Li-ion batteries are fast approaching their theoretical limit. Meanwhile, Lithium Sulphur (Li-S) batteries, owing to their ultrahigh theoretical energy density of about 2600 Whkg^-1, low-cost, Earth-abundant, and environmentally friendly sulfur (S) cathode, are seen as promising replacements to realize energy densities beyond 500 Whkg^-1. Despite these advantages, the large-scale implementation of Li-S technology has been stymied due to several issues, one of the most deleterious of them is the dissolution and shuttling of polysulfide intermediates during cycling resulting in severe self-discharge, lowered S utilization and coulombic efficiency. Over the past decades, substantial amount of research towards mitigating ‘polysulfide shuttling’ shuttling has been focused on cathodic modification strategies such as infiltration of S in porous carbon, metal oxide or conducting polymer scaffold matrix which retard the mobility and loss of active material. However, such simple confinement strategies have been shown to be lacking over long cycling due to the relatively weak intermolecular interactions between the host and polysulfide molecules. An effective solution comes in the form of engineering ‘sulfiphilic’ materials that adsorb polysulfide species. For example, surface modification of cathodes with rGO and functionalized carbon species have shown success in reducing the redox shuttling. However, these approaches require elaborate preparation and hence, are limited in their practical usage.

To overcome this, we propose a facile approach to improve cell performance via incorporation of functionalized graphenic species in the Li-S electrolyte. In this work, we have probed the impact of using tailored single-layer, heteroatom-doped graphene as electrolyte additives. We have studied the impact of their morphology and functionalization on the electrochemical performance of the cell. Results show a marked improvement in the discharge capacity and a high capacity retention of 84% over 105 cycles at 0.2 C cycling rate. The GCD cycle analysis showed an improvement in first cycle discharge plateau suggesting improved S utilization which was further substantiated by extensive postmortem analysis and polysulfide adsorption testing. Further, the electrolyte-modified cells showed an impressive three-fold and two-fold improvement in capacity at 1C and 2C cycling rates, respectively.

These results demonstrated that tailored heteroatom-doped graphene in the form of electrolyte additive is an effective strategy to improve electrochemical performance via enhanced polysulfide encapsulation, cell conductivity and anode stabilization. Finally, we will present the effect of heteroatom-doped graphenic species on mitigation of polysulfide shuttling and cell performance when they are incorporated in the gel electrolyte system.