Assembling organic-inorganic building blocks for high-capacity electrode design

Area of Science:

• Materials Science
• Electrochemistry
• Sustainable Energy Storage

Background:

• Metal-organic electrode materials show promise for electrochemical energy storage but often have limited capacity and stability due to few active sites.
• Activating transition metals and carbon rings can improve electron delocalization and performance in these materials.

Purpose of the Study:

• To develop a novel composite metal-organic material that synergistically activates inorganic and organic components for enhanced electrochemical energy storage.
• To investigate the FeF3(4,4 ombin-bpy) material as a high-capacity electrode for lithium-ion storage.

Main Methods:

• First-principles calculations (Density Functional Theory) were used to analyze redox processes and electronic structure.
• Electrochemical measurements were performed to evaluate the performance of the FeF3(4,4 ombin-bpy) electrode.

Main Results:

• The FeF3(4,4 ombin-bpy) composite material demonstrated an 8-electron transfer redox process, achieving a high specific capacity of 796.7 mA h g⁻¹.
• Calculations and experiments confirmed Fe ions, and C=C and C=N bonds as active sites for Li-ion storage, leading to high reversible capacity (793.1 mA h g⁻¹) and excellent rate capability.
• The material exhibited structural stability and a reduced band gap, with electronegative F-ions playing a crucial role in activating Fe3+ and C=C bonds.

Conclusions:

• Assembling inorganic-organic building blocks into composite materials is an effective strategy to activate both cationic and anionic redox sites for high-performance energy storage.
• FeF3(4,4 ombin-bpy) serves as a promising electrode material for lithium-ion batteries, offering high capacity and stability.
• This design principle can be extended to discover other high-capacity metal-organic electrode materials, such as MnF3(4,4 ombin-bpy) and VF3(4,4 ombin-bpy).