Cerium Oxide Nanocrystal Embedded Bimodal Micromesoporous Nitrogen-Rich Carbon Nanospheres as Effective Sulfur Host for Lithium-Sulfur Batteries.

Abstract

For developing lithium-sulfur (Li-S) batteries, it is critical to design advanced cathode materials with high sulfur loading/utilization ratios and strong binding interactions with sulfur species to prevent the dissolution of intermediate polysulfides. Here we report an effective sulfur host material prepared by implanting cerium oxide (CeO₂) nanocrystals homogeneously into well-designed bimodal micromesoporous nitrogen-rich carbon (MMNC) nanospheres. With the high conductivity and abundant hierarchical pore structures, MMNC nanospheres can effectively store and entrap sulfur species. Moreover, the inserted polar and electrocatalytically active CeO₂ nanocrystals and high nitrogen content of MMNC can synergistically solve the hurdle of the polysulfide dissolution and furthermore significantly promote stable redox activity. By combining these advantages, CeO₂/MMNC-S cathodes with 1.4 mg cm^-2 sulfur exhibit high reversible capacities (1066 mAh g^-1 at 0.2 C after 200 cycles and 836 mAh g^-1 at 1.0 C after 500 cycles), good rate capability (737 mAh g^-1 at 2.0 C), and high cycle stability (721 mAh g^-1 at 2.0 C after 1000 cycles with a low capacity decay of 0.024% per cycle). Furthermore, a high and stable reversible capacity of 611 mAh g^-1 is achieved after cycling for 200 cycles with higher sulfur loading of 3.4 mg cm^-2.