Thermal Modulation of MOF and Its Application in Lithium Sulfur Batteries.

Abstract

The applications of metal organic frameworks (MOFs) as sulfur hosts focus on the pristine MOFs and their carbonization products for establishing high performance lithium sulfur batteries (LSBs). However, the mecha-nism that modulate 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 the predeter-mined specific temperature by TG analysis and systematically investigate their microstructure and chemical character-istic evolution. The composite processed at 300 °C (U@rGO-P300) results in rearrangement of octahedral nano phase into an amorphous material while retaining a large number of functional groups of -NH2 and COO-, which leading to additional nano-structure interface and the high BET surface area of 298.4 m2 g-1. Moreover, the new created abundant sub oxidative Zr3+ atom sites serves as the polysulfide anchor and transfer mediator active sites. The assembled LSBs could deliver the capacity 906.1 and retain 801.7 mA h g-1 after 300 cycles at 1 C with a low value around 0.05% per cycle and the improved rate performance 619.1 mAh g-1 at 4C. The Li+ diffusion coefficients are significantly increased by 10-60 times. The work provides a simple route to activate the metal sites in MOF category with sub-oxidative state, lead-ing to the intriguing and unanticipated property.