Regulating Solvation Structure and Ion Transport via Lewis-Base Dual-Functional Covalent Organic Polymer Separators...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• High Li+ desolvation energy in lithium-metal anodes (LMAs) leads to dendrite growth and solid electrolyte interface (SEI) instability, hindering commercialization.
• Current LMA technologies face challenges with sluggish kinetics, poor ion transport, and limited cycle life.

Purpose of the Study:

• To develop a functionalized separator material that enhances lithium-ion transport and stability in LMAs.
• To investigate the effect of a novel covalent organic polymer on lithium plating/stripping behavior and SEI formation.

Main Methods:

• Design and synthesis of a Lewis-based N/O dual-functional covalent organic polymer (COP-DQCC) with carbonyl components.
• Integration of COP-DQCC into commercial polypropylene separators.
• Electrochemical performance testing (symmetric cells, LiFePO4/LMA cells) and in situ optical microscopy.
• Characterization using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and theoretical calculations.

Main Results:

• COP-DQCC enhances lithium salt dissociation and Li+ desolvation, reducing solvent transport and accelerating Li+ migration.
• The modified separator effectively inhibits lithium dendrite growth and promotes uniform lithium deposition.
• A stable, LiF-rich SEI layer is formed, regulating ion transport.
• Symmetric cells demonstrated stable cycling over 2400 h at 1.0 mA cm-2 and 900 h at 4.0 mA cm-2.
• LiFePO4/COP-DQCC@PP/Li cells showed excellent cycling stability, retaining 84.6% capacity after 1200 cycles at 1.0 C.

Conclusions:

• The COP-DQCC modified separator significantly improves the electrochemical performance and stability of LMAs.
• This approach offers a promising strategy for developing durable, dendrite-free anodes for high-energy-density batteries.
• The study highlights the potential of functionalized covalent organic polymers in advanced battery technologies.