Cooperative catalytic Mo-S-Co heterojunctions with sulfur vacancies for kinetically boosted lithium-sulfur battery

Abstract

The intelligent design of catalytic materials with unique architectures has a significant impact on regulating the polysulfides (LiPSs) conversion and boosting the performance of Li − S batteries. Here, starting from 2D catalytic MoS2 nanosheets and combined with the first-principle calculations, the covalent heterojunction and S vacancy are simultaneously developed in MoS2 to regulate the electronic structure and improve the LiPSs conversion kinetics. The S vacancy and heterojunction (MoS2-x-Co9S8-y) engineering can significantly improve the electrical conductivity of MoS2 by incorporating shallow donor levels into the MoS2. Moreover, the incorporation of Co9S8-y greatly improves the chemisorption ability of heterostructure towards LiPSs. The LiPSs are preferentially adsorbed at the catalytic Mo-S-Co heterojunction, where both Li+ and e- are easy to access. The coupled fast Li+/e- transportation of MoS2-x-Co9S8-y enables direct and fast LiPSs “adsorption-conversion” at the catalytic Mo-S-Co heterojunction with enhanced bidirectional catalytic properties. Due to the ingenious co-engineering of S vacancy and heterointerface, the Li − S cell with MoS2-x-Co9S8-y/rGO interlayer delivers high sulfur utilization (1382.5 mAh/g at 0.1C), excellent rate capability (710.2 mAh/g at 3C), and long cycle life over 600 cycles (0.06 % capacity decay per cycle). This work demonstrates the great potential of anion deficiency and heterojunction co-construction for high-performance Li − S batteries.