Energizing sulfur chemistry: Synergistic modulation of oxygen vacancies and heterointerface in MoO <sub>2– <i>x</i> </sub>-Mo <sub>2</sub>C@NC for long-lasting lithium-sulfur batteries
Xiaobo Qu, Hailong Xie, Na Li, Peng Wang, Xiaoyan An, Wei Zhang, Zaowen Zhao, Xiaodong Shi
Abstract
The practical deployment of lithium-sulfur (Li-S) batteries is impeded by severe polysulfide shuttle effects and sluggish redox kinetics. The use of heterostructures as catalysts in sulfur hosts is expected to improve the electrochemical performance of Li-S batteries. However, single heterostructures still suffer from the fatal problems of few active sites and high charge transfer barriers. Herein, defect-engineered MoO<sub>2</sub><sub>–<em>x</em></sub>-Mo<sub>2</sub>C@NC (NC is the abbreviation form of nitrogen-doped carbon) is designed as an efficient electrocatalyst to adjust the surface properties and electron distribution of the heterostructure by introducing a defective structure into the heterostructure, thereby enhance active site exposure. The <em>d</em>-orbitals of Mo<sub>2</sub>C facilitate strong interactions with the <em>p</em>-electrons of MoO<sub>2</sub>, enabling efficient electron transfer between reactants and active sites. DFT calculations confirm the interaction of the d orbitals of Mo<sub>2</sub>C with the p electrons in the MoO<sub>2</sub> material, effectively lowering the reaction energy barrier. As a result, the S/MoO<sub>2</sub><sub>–<em>x</em></sub>-Mo<sub>2</sub>C@NC exhibits remarkable cycle stability, retaining a specific capacity of 714 mAh·g<sup>–1</sup> after 500 cycles at 0.5 C. This work provides insights into defect-driven heterostructure design for advanced Li-S batteries.