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.
Keywords: Li−S batteries; cerium oxide; micromesoporous nitrogen-rich carbon nanospheres; physical and chemical confinement; shuttle effect.