MIL‐96‐Al for Li–S Batteries: Shape or Size?

• Published in: Advanced materials (Weinheim) 2022-01, Vol.34 (4), p.e2107836-n/a
• Main Authors: Geng, Pengbiao, Wang, Lei, Du, Meng, Bai, Yang, Li, Wenting, Liu, Yanfang, Chen, Shuangqiang, Braunstein, Pierre, Xu, Qiang, Pang, Huan
• Format: Article
• Language: English
• Subjects: Aluminum; Chemical Sciences; Density functional theory; hexagonal bipyramidal crystals; hexagonal platelet crystals; hexagonal prismatic bipyramidal crystals; Lithium sulfur batteries; Li–S batteries; Material chemistry; Materials science; Metal-organic frameworks; MIL‐96‐Al; Particle size; Platelet crystals; shuttle effect
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202107836

Metal–organic frameworks (MOFs) with controllable shapes and sizes show a great potential in Li–S batteries. However, neither the relationship between shape and specific capacity nor the influence of MOF particle size on cyclic stability have been fully established yet. Herein, MIL‐96‐Al with various shapes, forming hexagonal platelet crystals (HPC), hexagonal bipyramidal crystals (HBC), and hexagonal prismatic bipyramidal crystals (HPBC) are successfully prepared via cosolvent methods. Density functional theory (DFT) calculations demonstrate that the HBC shape with highly exposed (101) planes can effectively adsorb lithium polysulfides (LPS) during the charge/discharge process. By changing the relative proportion of the cosolvents, HBC samples with different particle sizes are prepared. When these MIL‐96‐Al crystals are used as sulfur host materials, it is found that those with a smaller size of the HBC shape deliver higher initial capacity. These investigations establish that different crystal planes have different adsorption abilities for LPS, and that the MOF particle size should be considered for a suitable sulfur host. More broadly, this work provides a strategy for designing sulfur hosts in Li–S batteries. MIL‐96‐Al crystals with hexagonal platelet crystal (HPC), hexagonal bipyramidal crystal (HBC), and hexagonal prismatic bipyramidal crystal (HPBC) shapes are successfully prepared by co‐solvent methods. Moreover, by changing the ratio of the cosolvent, different sizes of the HBC shape are prepared. These MIL‐96 crystals are used as sulfur hosts to investigate their ability to suppress the shuttle effect in Li–S batteries.