The applications of metal-organic frameworks (MOFs) as sulfur hosts focus on pristine MOFs and their carbonization products for establishing high-performance lithium-sulfur batteries (LSBs). However, the mechanism that modulates the specific nanostructures and the compositions at different treatment temperatures still needs further exploration. In this work, we modulate the pyrolysis products of UiO-66-NH2@rGO (U@rGO) at a predetermined specific temperature by thermogravimetric (TG) analysis and systematically investigate their microstructure and chemical characteristic evolution. The composite processed at 300 °C (U@rGO-P300) results in the rearrangement of an octahedral nanophase into an amorphous material while retaining a large number of functional groups of -NH2 and COO-, which lead to an additional nanostructure interface and a high Brunauer-Emmett-Teller (BET) surface area of 298.4 m2 g-1. Moreover, the newly created abundant suboxidative Zr3+ atom sites serve as the polysulfide anchor and transfer mediator active sites. The assembled LSBs could deliver a capacity of 906.1 and retain 801.7 mA h g-1 after 300 cycles at 1C with a low fading rate of around 0.05% per cycle and an improved rate performance of 619.1 mA h g-1 at 4C. The Li+ diffusion coefficients are significantly increased by 10-60 times. This work provides a simple route to activate the metal sites in the MOF category with a suboxidative state, leading to intriguing and unanticipated properties.
Keywords: active sites; electrode kinetics; metal−organic framework; polysulfide; thermal modulation.