MOF-derived Co–Mo bimetallic heterostructures for the selective trapping and conversion of polysulfides in lithium–sulfur batteries

Abstract

Lithium–sulfur batteries (LSBs) are promising energy storage systems, but their practical application is hindered by the polysulfide shuttle effect and slow redox kinetics. To address these challenges, we constructed ZIF-67@CoS_x/MoO₃ with a core–shell structure and CoS_x/MoO₃ with a hollow structure as separator-modified materials for LSBs by varying the degree of sulfidation of ZIF-67. The high intrinsic conductivity of CoS_x facilitated ion transfer between the cathode and separator. Additionally, the introduction of MoO₃ formed a heterogeneous structure with CoS_x that enhanced the adsorption of LiPSs. Via in situ UV-vis and electrochemical impedance spectroscopy testing, we demonstrated the preferred selective trapping and conversion of LiPSs by CoS_x/MoO₃. As a result of the synergistic effect of the bimetallic heterogeneous structure, the modified LSB exhibited excellent cycling stability, with a capacity decay rate of only 0.041% after 500 cycles at 1C. Moreover, it achieved a high discharge capacity of 632 mA h g⁻¹ at 2C. This work provides a novel concept for MOF-derived heterogeneous structures to be applied in high-performance LSBs.