Suppressed polysulfide crossover in Li−S batteries through a high-flux graphene oxide membrane supported on a sulfur cathode

Utilization of permselective membranes holds tremen-dous promise for retention of the electrode-active material in electrochemical devices that suffer from electrode instability issues. In a rechargeable Li−S battery--a strong contender to outperform the Li-ion technologymigration of lithium polysulfides from the sulfur cathode has been linked to rapid capacity fading and lower Coulombic efficiency. However, the current approaches for configuring Li−S cells with permselective membranes suffer from large ohmic polarization, resulting in low capacity and poor rate capability. To overcome these issues, we report the facile fabrication of a high-flux graphene oxide membrane directly onto the sulfur cathode by shear alignment of discotic nematic liquid crystals of graphene oxide (GO). In conjunction with a carbon-coated separator, the highly ordered structure of the thin (∼0.75 µm) membrane and its inherent surface charge retain a majority of the polysulfides, enabling the cells to deliver very high initial discharge capacities of 1063 and 1182 mAh g^-1_electrode for electrodes with 70 and 80% sulfur content, respectively, at the practical 0.5 C rate. The very high sulfur utilization and impressive capacity retentions of the high sulfur content electrodes result in some of the highest performance metrics in the literature of Li−S (e.g., electrode capacity of 835 mAh g^-1_electrode after 100 cycles at 0.5 C with a sulfur content of 80%). We show that the structural order of the shear-aligned GO membrane is key in maintaining good kinetics of the charge transfer processes in Li-S batteries.