Reasonably Introduced ZnIn₂S₄@C to Mediate Polysulfide Redox for Long-Life Lithium-Sulfur Batteries

In consideration of the inferior rate performance and low sulfur utilization of lithium-sulfur batteries (LSBs), an effective strategy via combining polar materials with the conductive carbon sulfur host is widely applied. Herein, metal organic framework-derived in situ-developed ZnIn₂S₄@C is innovatively synthesized to mediate lithium polysulfide (LPS) conversion based on high electron conductivity and strong chemical interactions for advanced LSBs. Polar ZnIn₂S₄ possesses strong chemisorption in keeping with the DFT calculation results and catalytic for LPSs, ensuring a high sulfur utilization. Meanwhile, the hollow non-polar carbon frame possessing hierarchical pores not only provides internal space to contain active species but also accommodates efficient electronic transferring and diffusion of lithium ions in the process of cycling. The above advantages make the electrode possess promising stability and good rate performances, achieving long-term and high-rate cycling. Thus, under a sulfur loading of 1.5 mg cm^-2, after 500 cycles, at 2 and 5 C, the as-prepared ZnIn₂S₄@C@S delivers reversible capacities of 734 mA h g^-1 (75.7% of the initial capacity with a dropping rate of 0.015% per cycle) and 504 mA h g^-1 (68.5% of the primal capacity with a dropping rate of 0.029% per cycle), respectively. Even at a high sulfur loading of 5.0 mg cm^-2, at 5 C, 65.6% of the initial capacity can be maintained with a low fading rate of 0.430% per cycle after 500 loops with a high Coulombic efficiency of around 99.8%.