Metal-organic framework MIL-101(Fe)–NH₂ as an efficient host for sulphur storage in long-cycle Li–S batteries

Porous metal-organic framework (MOF) MIL-101(Fe)–NH₂ was synthesized, characterized and used as a host material for sulphur in the context of lithium-sulphur batteries. The MIL-101(Fe)–NH₂ support possessed, a large surface area, close to 3500 m² g⁻¹, and mild framework stability up to 120 °C. As the framework stability strongly depends on the presence of guests in the micro/mesoporous cages, conditions for sulphur inclusion process were carefully selected, and then the material was further carbonized. MOF as a conductive part of cathode material displayed successful sulphur capture and encapsulation. The encapsulation of sulphur was accompanied by highly stable charge/discharge cycle performances and high efficiency. Consequently, the cathode showed at a current rate 0.5C a high initial discharge capacity of 705 mA h g⁻¹ and after 200 cycles of 476 mA h g⁻¹, corresponding to a low fading rate of 0.162% per cycle. The capacity of the cycle after self-discharge was 94.8% of the capacity in the cycle before self-discharge.