MOF-derived micro-mesoporous TiO2-based composite as sulfur host for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) battery is a promising high-energy density device. However, the shuttling of lithium polysulfide (LiPS) and severe volume variation of sulfur has hindered its practical application. Herein, a nitrogendoped micro-mesoporous Co/NC-TiO2 composite derived from cobalt-doped MIL-125 is prepared as efficient multifunctional sulfur host. In the design of this composite, abundant micro-mesoporous structure is introduced by cobalt ion etching and ammonia treatment, which affords sufficient space for sulfur loading and adapts to large volume variation. Meanwhile, the polar TiO2 endows the composite with high sulfur affinity, and the introduction of cobalt offers strong LiPS adsorption and fast redox reaction kinetics. Accordingly, the Co/NCTiO2 electrode achieves a specific capacity of 941 mAh g-1 at 1 C and a low capacity decay rate of 0.062% per cycle after 500 cycles. It is also capable of delivering a high capacity of 730 mAh g-1 at 3 C. At sulfur loading of 5.5 mg cm-2, the Co/NC-TiO2 electrode provides a high areal initial capacity of 5.6 mAh cm-2, showing promising application in Li-S batteries.

Automated summary

A nitrogen-doped micro-mesoporous Co/NC-TiO2 composite is synthesized as an efficient multifunctional sulfur host, addressing the issues of lithium polysulfide shuttling and sulfur volume variation. The composite possesses abundant micro-mesoporous structure for sulfur loading, high sulfur affinity from polar TiO2, and strong LiPS adsorption and fast redox reaction kinetics from the introduction of cobalt. The Co/NC-TiO2 electrode exhibits high specific capacity at different rates and low capacity decay rate, making it a promising candidate for Li-S batteries.