Metal-organic-framework-derived N-C-Co film as a shuttle-suppressing interlayer for lithium sulfur battery

Owing to its high theoretical capacity and energy density, lithium sulfur battery represents one of the most promising candidates for future energy storage. However, the dissolution of polysulfide in the electrodes results in shuttle effect and rapid fading of capacity, which impedes practical application of lithium sulfur battery. To inhibit the shuttle effect, in this work, an integrated, highly conductive metal-organic-framework-derived porous nitrogen-carbon-cobalt (N-C-Co) interlayer is designed and prepared to suppress polysulfides lost in electrolyte. Owing to the novel MOFs precursor, N-C-Co composite possesses hierarchical pores, pyridinic and pyrrolic nitrogen groups. This coating interlayer acts effectively through three aspects: as a physical blocking layer to prevent most polysulfides from dissolving out of the cathode, physical and chemical adsorption to confine free polysulfides in the electrolyte, and a second pseudo-upper current collector to enhance the utilization of sulfur. As a result, the improvement of battery performance is achieved by the well-designed interlayer. The initial discharge capacity of composite cathode with the interlayer is 1216.9 mAh g−1 at 1C and can retain capacity of 660.3 mAh g−1 after 250 cycles at the sulfur loading of 1.5 mg cm−2. At the same time, the Coulombic efficiency maintains above 99% during cycling, demonstrating an effective inhibition of the shuttle effect. Even at a high sulfur mass loading of 5.2 mg cm−2, the battery can still deliver 678.8 mAh g−1 after 50 cycles and an areal discharge capacity is of above 3.53 mAh cm−2.