(78b) Rational Design of the Cathode Materials in the Lithium-Sulfur Batteries

Rational design of the sulfur electrode is essential to solve several practical problems in lithium–sulfur batteries. Great progress has been made by using carbon-based nanostructures for physically and chemically confining soluble polysulfide, however, the underlying mechanism remains unclear. Here using density functional theory calculations, we show that the interfacial interaction between Li₂S₈ – a typical lithium polysulfide formed at the beginning of discharge – and the oxygen/nitrogen modified graphitic surface and edges. Our results indicate that N and O impurities play a significant role in chemically stabilizing lithium polysulfide, which are otherwise soluble, onto the carbon surface. In addition, we find that O and N functional groups can work synergistically by forming the N-C-O complex, which can enhance the interfacial binding. Moreover, we show that, by manipulating the wettability of the cathode surface using oxygen-containing hydrophilic species, adsorption of the polysulfide and electronic conductivity can be controlled to improve the performance.

Acknowledgements: The calculations were performed at NERSC and OU Supercomputing Center for Education and Research (OSCER). We thank support from the U.S. DOE through a DOE/EPSCOR grant (DESC0004600).