Oxygen Vacancies‐Rich CeO_2–<i>_X</i> Nanocrystalline Embedded in N‐Doped Carbon Matrix toward High‐Performance Lithium–Sulfur Batteries

The sluggish redox kinetics of lithium polysulfides (LiPSs) and their shuttle behavior are regarded as the key issues to the commercial application of lithium-sulfur (Li-S) batteries. Here, a novel LiPSs immobilizer and catalytic promoter is proposed by introducing oxygen-vacancy-rich cerium dioxide (CeO_2- _X) nanocrystalline embedded in a N-doped carbon skeleton (CeO_2- _X@NC) and investigated as a modified separator in Li-S batteries. Density functional theory calculations, UV-vis diffusion reflection spectra, and X-ray photoelectron spectroscopy indicate that introducing oxygen vacancies can tailor the intrinsic electron band structure of CeO_2- _X nanocrystalline, which is able to improve their electron and ion conductivity. This leads to enhanced polysulfides adsorption and realize targeted acceleration of redox conversion kinetics for LiPSs. In return, the sulfur cathodes based on CeO_2- _X@NC demonstrate both stable long-lifespan cyclability (over 1000 cycles at 4 C) and superior rate performance (up to 4 C). Additionally, a high areal capacity of 5.61 mAh cm^-2 at a sulfur loading of 7.09 mg cm^-2 is also achieved. This work underscores the imperative of incorporating defect and heterostructure engineering to enhance the fast charge-discharge capability and stability of Li-S batteries, offering a new approach for their potential applications.