3D Crown Ether Covalent Organic Framework as Interphase Layer toward High-Performance Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium metal batteries face challenges from dendrite formation and active lithium consumption, limiting their practical use.
• Artificial solid-electrolyte interphase (SEI) layers, like 2D covalent organic frameworks (COFs), are explored to mitigate these issues.
• The potential of 3D COFs as protective layers is underexplored due to concerns about disordered dendrite growth.

Purpose of the Study:

• To investigate the efficacy of a 3D crown ether-based COF with ffc topology as an interphase layer for lithium anodes.
• To address the preconception that 3D COFs might promote disordered lithium dendrite growth.
• To explore the impact of oriented crown ether units on lithium-ion transport and deposition.

Main Methods:

• Fabrication of a 3D crown ether-based COF with parallel and vertical orientation of crown ether units.
• Electrochemical characterization of Li/COF-Cu cells to evaluate performance metrics.
• Analysis of lithium-ion diffusion kinetics and deposition behavior with the COF interphase.

Main Results:

• The 3D COF interphase facilitated homogeneous Li+ flux and smooth Li deposition in a 3D direction due to strong crown ether-Li+ coupling.
• Achieved a high Li+ transference number of 0.85.
• Demonstrated a low Li-nucleation overpotential (17.4 mV) and high average Coulombic efficiency (≈98.6%) over 340 cycles.

Conclusions:

• 3D covalent organic frameworks can be effectively designed as protective interphase layers for lithium metal anodes.
• The oriented crown ether units in the 3D COF promote uniform lithium deposition and enhance battery cycling stability.
• This study offers a new perspective for designing advanced COFs in energy storage applications.