Multimodal Engineering of Catalytic Interfaces Confers Multi-Site Metal-Organic Framework for Internal Preconcentration and Accelerating Redox Kinetics in Lithium-Sulfur Batteries.

The development of highly efficient catalysts to address the shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) in lithium-sulfur batteries (LSBs) remains a formidable challenge. In this study, a series of multi-site catalytic metal-organic frameworks (MSC-MOFs) were elaborated through multimodal molecular engineering to regulate both the reactant diffusion and catalysis processes. MSC-MOFs were crafted with nanocages featuring collaborative specific adsorption/catalytic interfaces formed by exposed mixed-valence metal sites and surrounding adsorption sites. This design facilitates internal preconcentration, a coadsorption mechanism, and continuous efficient catalytic conversion toward polysulfides concurrently. Leveraging these attributes, LSBs with an MSC-MOF-Ti catalytic interlayer demonstrated a 62 % improvement in discharge capacity and cycling stability. This resulted in achieving a high areal capacity (11.57 mAh cm-2 ) at a high sulfur loading (9.32 mg cm-2 ) under lean electrolyte conditions, along with a pouch cell exhibiting an ultra-high gravimetric energy density of 350.8 Wh kg-1 . Lastly, this work introduces a universal strategy for the development of a new class of efficient catalytic MOFs, promoting SRR and suppressing the shuttle effect at the molecular level. The findings shed light on the design of advanced porous catalytic materials for application in high-energy LSBs.

Balanced Mass Transfer and Active Sites Density in Hierarchical Porous Catalytic Metal-Organic Framework for Enhancing Redox Reaction in Lithium-Sulfur Batteries.

Developing highly efficient catalysts, characterized by controllable pore architecture and effective utilization of active sites, is paramount in addressing the shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) in lithium-sulfur batteries (LSBs), which, however, remains a formidable challenge. In this study, a hierarchical porous catalytic metal-organic framework (HPC-MOF) with both appropriate porosity and abundant exposed catalytic sites is achieved through time-controlled precise pore engineering. It is revealed that the evolution of the porous structure and catalytic site density is time-dependent during the etching processes. The moderately etched HPC-MOF-M attains heterogeneous pores at various scales, where large apertures ensure fast mass transfer and micropores inherit high-density catalytic sites, enhancing utilization and catalytic kinetics at internal catalytic sites. Capitalizing on these advantages, LSB incorporating the HPC-MOF-M interlayer demonstrates a 164.6% improvement in discharge capability and an 83.3% lower decay rate over long-term cycling at 1.0C. Even under high sulfur loading of 7.1 mg cm-2 and lean electrolyte conditions, the LSB exhibits stable cycling for over 100 cycles. This work highlights the significance of balancing the relationship between mass transfer and catalytic sites through precise chemical regulation of the porous structure in catalytic MOFs, which are anticipated to inspire the development of advanced catalysts for LSBs.

Molten Guest-Mediated Metal-Organic Frameworks Featuring Multi-Modal Supramolecular Interaction Sites for Flame-Retardant Superionic Conductor in All-Solid-State Batteries.

The development of solid-state electrolytes (SSEs) with outstanding comprehensive performance is currently a critical challenge for achieving high energy density and safer solid-state batteries (SSBs). In this study, a strategy of nano-confined in situ solidification is proposed to create a novel category of molten guest-mediated metal-organic frameworks, named MGM-MOFs. By embedding the newly developed molten crystalline organic electrolyte (ML20) into the nanocages of anionic MOF-OH, MGM-MOF-OH, characterized by multi-modal supramolecular interaction sites and continuous negative electrostatic environments within nano-channels, is achieved. These nanochannels promote ion transport through the successive hopping of Li+ between neighbored negative electrostatic environments and suppress anion movement through the chemical constraint of the hydroxyl-functionalized pore wall. This results in remarkable Li+ conductivity of 7.1 × 10-4 S cm-1 and high Li+ transference number of 0.81. Leveraging these advantages, the SSBs assembled with MGM-MOF-OH exhibit impressive cycle stability and a high specific energy density of 410.5 Wh kganode + cathode + electrolyte -1 under constrained conditions and various working temperatures. Unlike flammable traditional MOFs, MGM-MOF-OH demonstrates high robustness under various harsh conditions, including ignition, high voltage, and extended to humidity.