Double MOF derived Co2Mo3O8-MoO2 nanorod cluster heterostructure as separator-mediator for high performance lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are regarded as potential candidates for next-generation energy storage technologies, however, their practical applications are limited by the dual constraints of shuttle effect of lithium polysulfides (LiPSs) and slow catalytic reaction kinetics. To address these issues, a metal-organic framework (MOF)-derived composite Co 2 Mo 3 O 8 -MoO 2 heterojunction (Mo-Co@C) loaded on carbon nanorod clusters was designed. The heterojunction showed a low d -band center level and higher d -band density of state (DOS), and the inside built-in electric field can significantly enhance the adsorption of LiPSs and effectively inhibit the occurrence of the shuttle effect. In addition, the nanorod-like cluster formed by the self-assembly process of bimetallic organic framework exhibits a high specific surface area, which not only provided more active centers, but also the transport channel for lithium ions migration, and promoted the enhancement of the redox reaction kinetics simultaneously. The battery with the Mo-Co@C composites as a separator-mediator exhibited initial discharge capacity of 895.7 mAh g −1 at 1 C, and it still maintains a reversible capacity of 402.4 mAh g −1 after 1000 cycles, which corresponds to a capacity degradation rate of 0.055% per cycle. The capacity can still reach 501.3 mAh g −1 at 0.5 C even at a low-temperature of −20 °C. This work provides new insights for the design of catalysts for high-performance lithium-sulfur batteries.