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.