Cerium Oxysulfide with O-Ce-S Bindings for Efficient Adsorption and Conversion of Lithium Polysulfide in Li-S Batteries.

Understanding of adsorption and kinetic conversion of polysulfide lithium (LiPSs) in Li-S batteries is quite crucial for the design of efficient effective sulfur carriers. Herein, based on the possible interactions with LiPSs, Ce2O2S with unique O-Ce-S bindings is proposed to be used as a promising carrier additive and a 2D Ce2O2S/C composite is synthesized via a one-facile NaCl-template method and subsequent sulfuration under 700 °C. The 2D Ce2O2S/C exhibits a stronger adsorption capability than CeO2/C through the adsorption test for Li2S6. Combined with XPS and DFT results, the superiority is mainly originated from the formation of S-S and Li-S bonds between LiPSs and the lattice S on the surface of Ce2O2S. The 2D Ce2O2S/C composite also exhibits a better catalytic ability than CeO2 according to the change of the free energies of the polysulfides during the discharge process, which coincides with the lower oxidation potential for Li2S2/Li2S transition by cyclic voltammetry. Resultantly, the cathodes using the Ce2O2S/C composite as a carrier manifest an enhanced rate and cycling performances. Hence, our work paves a phenomenon wherein Ce2O2S with O-Ce-S bindings is more beneficial to improve the cycling stability of Li-S batteries than CeO2 containing single Ce-O bonds, which may be also suitable for other kinds of metallic sulfur oxide compounds.