MgCo layered double hydroxide-based yolk shell polyhedrons as multifunctional sulfur mediator for lithium-sulfur batteries.

The development of efficient sulfur host materials to address the shuttle effect issues of lithium polysulfides (LiPSs) is crucial in the lithium-sulfur (Li-S) batteries, but still challenging. In the present study, a novel yolk shell structured MgCo-LDH/ZIF-67 composite is designed as Li-S battery cathode. In this composite, the shell layer is MgCo layered double hydroxide constructed by partially etching ZIF-67 nanoparticle by Mg2+, and the core is the unreacted ZIF-67 particle. The unique yolk shell structure not only provides abundant pores for sulfur accommodation, but also facilitates the electrolyte penetration and ion transport. The ZIF-67 core exhibits strong polar adsorption to LiPSs through the Lewis acid-base interactions, and the micropores/mesoporous can further trap LiPSs. Meanwhile, the MgCo-LDH shell exposes enough sulfur-philic sites for enhancing chemisorption and catalyzes the LiPSs conversion. As a result, when MgCo-LDH/ZIF-67 is used as sulfur host in the cathode, the cell achieves a high discharge capacity of 1121 mAh g-1 at 0.2 C, and an areal capacity of 5.0 mAh cm-2 under the high sulfur loading of 5.8 mg cm-2. The S/MgCo-LDH/ZIF-67 electrode holds a promising potential for the development of Li-S batteries.