MOF-derived 3D hierarchical porous TiO2 @ NPC @ S as high-performance cathodes for Li-S batteries

Abstract

The capacity of traditional lithium-ion batteries has approached theoretical limits, and exploring lithium-sulfur batteries (LSBs) with high capacity and energy density is highly desired. Metal–organic framework (MOF)-derived materials are among the most crucial candidates for LSBs. The objectives of present work are improving the electrical conductivity, slowing down the volume expansion, and inducing the notorious “shuttle effect”. In this work, we developed MOF-derived nanoporous carbon (NPC)-coated composite TiO2@NPC as ideal sulfur host for Li-S batteries. The NPC offers sufficient space for the expansion of sulfur volume during electrochemical cycling process, while forming a conductive framework to promote the transport of ion and electron. High sulfur loading of 64.09% was obtained through both physical and chemical strategies. The TiO2@NPC@S cathode with multifunctional effects exhibits outstanding long-term cycling performance, presenting an initial capacity of up to 1327.35 mAh/g at 0.5 C with an average capacity decrease of 0.18% per cycle. It exhibits commendable rate capabilities, achieving 928 mAh/g at 1 C and 743 mAh/g at 1.5 C. The electrochemical performance of the synthesized TiO2@NPC@S is significant superior to the commercial Y-50@S materials. This work provides a successful approach for designing novel high-performance cathodes in LSBs.

Keywords

• lithium-sulfur battery
• metal–organic frameworks
• sulfur composites