Defect-Tailoring Metal-Organic Frameworks for Highly Fast-Charging Quasi-Solid-State Electrolytes Lithium Metal...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) offer tunable nanoporous structures for quasi-solid-state electrolytes (QSSEs).
• Limited Li+ dissociation and ionic conductivity in MOF-QSSEs hinder their use in high-energy-density batteries due to insufficient active sites.

Purpose of the Study:

• To enhance the performance of hafnium-based MOFs in QSSEs through defect engineering.
• To improve Li+ dissociation and ionic conductivity by increasing open metal site (OMS) density and optimizing the pore environment.

Main Methods:

• Employed defect engineering to modulate hafnium-based MOFs, increasing OMS density.
• Optimized the pore microenvironment and enhanced Lewis acid strength of OMSs.
• Investigated Li+ dissociation, anion (TFSI-) chemisorption, and ionic conductivity.

Main Results:

• Achieved an ionic conductivity of 1.0 mS cm-1 at 30 °C and a critical current density of 2 mA cm-2 in the defect-engineered Hf-MOF-QSSE.
• Demonstrated excellent cycling stability in Li||LiFePO4 cells (93% capacity retention after 1500 cycles at 10C).
• Showcased high rate capability in Li||NCM811 cells (85 mAh g-1 after 600 cycles at 5C).

Conclusions:

• Defect engineering is pivotal for optimizing MOF-based QSSEs by enhancing OMS density and Lewis acidity.
• The engineered Hf-MOF-QSSE surpasses previous MOF-QSSEs in ionic conductivity and critical current density.
• This strategy enables high-energy-density batteries with superior cycling stability and rate capability.